remote_billing: Implement confirmation flow for RemoteRealm auth.

The way the flow goes now is this:
1. The user initiaties login via "Billing" in the gear menu.
2. That takes them to `/self-hosted-billing/` (possibly with a
   `next_page` param if we use that for some gear menu options).
3. The server queries the bouncer to give the user a link with a signed
   access token.
4. The user is redirected to that link (on `selfhosting.zulipchat.com`).
Now we have two cases, either the user is logging in for the first time
and already did in the past.
If this is the first time, we have:
5. The user is asked to fill in their email in a form that's shown,
   pre-filled with the value provided inside the signed access token.
   They POST this to the next endpoint.
6. The next endpoint sends a confirmation email to that address and asks
   the user to go check their email.
7. The user clicks the link in their email is taken to the
   from_confirmation endpoint.
8. Their initial RemoteBillingUser is created, a new signed link like in
   (3) is generated and they're transparently taken back to (4),
   where now that they have a RemoteBillingUser, they're handled
   just like a user who already logged in before:
If the user already logged in before, they go straight here:
9. "Confirm login" page - they're shown their information (email and
   full_name), can update
   their full name in the form if they want. They also accept ToS here
   if necessary. They POST this form back to
   the endpoint and finally have a logged in session.
10. They're redirected to billing (or `next_page`) now that they have
    access.

confirmation/models.py

@@ -31,7 +31,10 @@ from zerver.models import (
 )
 
 if settings.ZILENCER_ENABLED:
-    from zilencer.models import PreregistrationRemoteServerBillingUser
+    from zilencer.models import (
+        PreregistrationRemoteRealmBillingUser,
+        PreregistrationRemoteServerBillingUser,
+    )
 
 
 class ConfirmationKeyError(Exception):
@@ -68,7 +71,9 @@ NoZilencerConfirmationObjT: TypeAlias = Union[
     RealmReactivationStatus,
 ]
 ZilencerConfirmationObjT: TypeAlias = Union[
-    NoZilencerConfirmationObjT, "PreregistrationRemoteServerBillingUser"
+    NoZilencerConfirmationObjT,
+    "PreregistrationRemoteServerBillingUser",
+    "PreregistrationRemoteRealmBillingUser",
 ]
 
 ConfirmationObjT = Union[NoZilencerConfirmationObjT, ZilencerConfirmationObjT]
@@ -197,6 +202,7 @@ class Confirmation(models.Model):
     REALM_CREATION = 7
     REALM_REACTIVATION = 8
     REMOTE_SERVER_BILLING_LEGACY_LOGIN = 9
+    REMOTE_REALM_BILLING_LEGACY_LOGIN = 10
     type = models.PositiveSmallIntegerField()
 
     class Meta:
@@ -237,6 +243,9 @@ if settings.ZILENCER_ENABLED:
     _properties[Confirmation.REMOTE_SERVER_BILLING_LEGACY_LOGIN] = ConfirmationType(
         "remote_billing_legacy_server_from_login_confirmation_link"
     )
+    _properties[Confirmation.REMOTE_REALM_BILLING_LEGACY_LOGIN] = ConfirmationType(
+        "remote_realm_billing_from_login_confirmation_link"
+    )
 
 
 def one_click_unsubscribe_link(user_profile: UserProfile, email_type: str) -> str:

corporate/lib/remote_billing_util.py

@@ -28,6 +28,7 @@ class RemoteBillingIdentityDict(TypedDict):
     remote_server_uuid: str
     remote_realm_uuid: str
 
+    remote_billing_user_id: Optional[int]
     authenticated_at: int
     uri_scheme: Literal["http://", "https://"]
 
@@ -133,9 +134,8 @@ def get_remote_server_and_user_from_session(
     request: HttpRequest,
     server_uuid: str,
 ) -> Tuple[RemoteZulipServer, Optional[RemoteServerBillingUser]]:
-    identity_dict = cast(
+    identity_dict: Optional[LegacyServerIdentityDict] = get_identity_dict_from_session(
-        Optional[LegacyServerIdentityDict],
+        request, realm_uuid=None, server_uuid=server_uuid
-        get_identity_dict_from_session(request, realm_uuid=None, server_uuid=server_uuid),
     )
 
     if identity_dict is None:

corporate/tests/test_remote_billing.py

@@ -33,6 +33,10 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
         next_page: Optional[str] = None,
         expect_tos: bool = True,
         confirm_tos: bool = True,
+        first_time_login: bool = True,
+        # This only matters if first_time_login is True, since otherwise
+        # there's no confirmation link to be clicked:
+        return_without_clicking_confirmation_link: bool = False,
     ) -> "TestHttpResponse":
         now = timezone_now()
 
@@ -45,12 +49,61 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
         self.assertEqual(result.status_code, 302)
         self.assertIn("http://selfhosting.testserver/remote-billing-login/", result["Location"])
 
-        # We've received a redirect to an URL that will grant us an authenticated
-        # session for remote billing.
         signed_auth_url = result["Location"]
+        signed_access_token = signed_auth_url.split("/")[-1]
         with time_machine.travel(now, tick=False):
             result = self.client_get(signed_auth_url, subdomain="selfhosting")
-        # When successful, we see a confirmation page.
+
+        if first_time_login:
+            self.assertFalse(RemoteRealmBillingUser.objects.filter(user_uuid=user.uuid).exists())
+            # When logging in for the first time some extra steps are needed
+            # to confirm and verify the email address.
+            self.assertEqual(result.status_code, 200)
+            self.assert_in_success_response(["Enter your email address"], result)
+            self.assert_in_success_response([user.realm.host], result)
+            self.assert_in_success_response(
+                [f'action="/remote-billing-login/{signed_access_token}/confirm/"'], result
+            )
+
+            with time_machine.travel(now, tick=False):
+                result = self.client_post(
+                    f"/remote-billing-login/{signed_access_token}/confirm/",
+                    {"email": user.delivery_email},
+                    subdomain="selfhosting",
+                )
+            self.assertEqual(result.status_code, 200)
+            self.assert_in_success_response(
+                ["To complete the login process, check your email account", user.delivery_email],
+                result,
+            )
+            confirmation_url = self.get_confirmation_url_from_outbox(
+                user.delivery_email,
+                url_pattern=(
+                    f"{settings.SELF_HOSTING_MANAGEMENT_SUBDOMAIN}.{settings.EXTERNAL_HOST}"
+                    r"(\S+)>"
+                ),
+                email_body_contains="Click the link below to complete the login process",
+            )
+            if return_without_clicking_confirmation_link:
+                return result
+
+            with time_machine.travel(now, tick=False):
+                result = self.client_get(confirmation_url, subdomain="selfhosting")
+
+            remote_billing_user = RemoteRealmBillingUser.objects.latest("id")
+            self.assertEqual(remote_billing_user.user_uuid, user.uuid)
+            self.assertEqual(remote_billing_user.email, user.delivery_email)
+
+            # Now we should be redirected again to the /remote-billing-login/ endpoint
+            # with a new signed_access_token. Now that the email has been confirmed,
+            # and we have a RemoteRealmBillingUser entry, we'll be in the same position
+            # as the case where first_time_login=False.
+            self.assertEqual(result.status_code, 302)
+            self.assertTrue(result["Location"].startswith("/remote-billing-login/"))
+            result = self.client_get(result["Location"], subdomain="selfhosting")
+
+        # Final confirmation page - just confirm your details, possibly
+        # agreeing to ToS if needed and an authenticated session will be granted:
         self.assertEqual(result.status_code, 200)
         self.assert_in_success_response(["Log in to Zulip server billing"], result)
         self.assert_in_success_response([user.realm.host], result)
@@ -67,6 +120,7 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
             return result
 
         # Verify the authed data that should have been stored in the session.
+        remote_billing_user = RemoteRealmBillingUser.objects.get(user_uuid=user.uuid)
         identity_dict = RemoteBillingIdentityDict(
             user=RemoteBillingUserDict(
                 user_email=user.delivery_email,
@@ -75,6 +129,7 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
             ),
             remote_server_uuid=str(self.server.uuid),
             remote_realm_uuid=str(user.realm.uuid),
+            remote_billing_user_id=remote_billing_user.id,
             authenticated_at=datetime_to_timestamp(now),
             uri_scheme="http://",
             next_page=next_page,
@@ -189,6 +244,7 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
                 desdemona,
                 expect_tos=True,
                 confirm_tos=False,
+                first_time_login=False,
             )
             self.assert_json_error(result, "You must accept the Terms of Service to proceed.")
 
@@ -196,6 +252,7 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
                 desdemona,
                 expect_tos=True,
                 confirm_tos=True,
+                first_time_login=False,
             )
         remote_billing_user.refresh_from_db()
         self.assertEqual(remote_billing_user.user_uuid, desdemona.uuid)
@@ -252,6 +309,7 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
                 # ToS has already been confirmed earlier.
                 expect_tos=False,
                 confirm_tos=False,
+                first_time_login=False,
             )
             self.assertEqual(result["Location"], f"/realm/{realm.uuid!s}/plans/")
             result = self.client_get(result["Location"], subdomain="selfhosting")
@@ -353,6 +411,28 @@ class RemoteBillingAuthenticationTest(BouncerTestCase):
                 ["Upgrade", "Purchase Zulip", "Your subscription will renew automatically."], result
             )
 
+    @responses.activate
+    def test_remote_billing_authentication_flow_cant_access_billing_without_finishing_confirmation(
+        self,
+    ) -> None:
+        self.login("desdemona")
+        desdemona = self.example_user("desdemona")
+        realm = desdemona.realm
+
+        self.add_mock_response()
+
+        result = self.execute_remote_billing_authentication_flow(
+            desdemona,
+            expect_tos=True,
+            confirm_tos=False,
+            first_time_login=True,
+            return_without_clicking_confirmation_link=True,
+        )
+        result = self.client_get(f"/realm/{realm.uuid!s}/billing/", subdomain="selfhosting")
+        # Access is not allowed. The user doesn't have an IdentityDict in the session, so
+        # we can't do a nice redirect back to their original server.
+        self.assertEqual(result.status_code, 401)
+
 
 class LegacyServerLoginTest(BouncerTestCase):
     @override

corporate/urls.py

@@ -35,7 +35,9 @@ from corporate.views.remote_billing_page import (
     remote_billing_legacy_server_confirm_login,
     remote_billing_legacy_server_from_login_confirmation_link,
     remote_billing_legacy_server_login,
+    remote_realm_billing_confirm_email,
     remote_realm_billing_finalize_login,
+    remote_realm_billing_from_login_confirmation_link,
 )
 from corporate.views.session import (
     start_card_update_stripe_session,
@@ -186,6 +188,15 @@ urlpatterns = list(i18n_urlpatterns)
 
 urlpatterns += [
     path("remote-billing-login/<signed_billing_access_token>", remote_realm_billing_finalize_login),
+    path(
+        "remote-billing-login/<signed_billing_access_token>/confirm/",
+        remote_realm_billing_confirm_email,
+    ),
+    path(
+        "remote-billing-login/do_confirm/<confirmation_key>",
+        remote_realm_billing_from_login_confirmation_link,
+        name="remote_realm_billing_from_login_confirmation_link",
+    ),
     # Remote server billing endpoints.
     path("realm/<realm_uuid>/plans/", remote_realm_plans_page, name="remote_realm_plans_page"),
     path(

corporate/views/remote_billing_page.py

@@ -1,5 +1,5 @@
 import logging
-from typing import Any, Dict, Literal, Optional
+from typing import Any, Dict, Literal, Optional, Union, cast
 from urllib.parse import urlsplit, urlunsplit
 
 from django.conf import settings
@@ -42,6 +42,7 @@ from zerver.lib.send_email import FromAddress, send_email
 from zerver.lib.timestamp import datetime_to_timestamp
 from zerver.lib.typed_endpoint import PathOnly, typed_endpoint
 from zilencer.models import (
+    PreregistrationRemoteRealmBillingUser,
     PreregistrationRemoteServerBillingUser,
     RemoteRealm,
     RemoteRealmBillingUser,
@@ -86,6 +87,7 @@ def remote_realm_billing_entry(
         ),
         remote_server_uuid=str(remote_server.uuid),
         remote_realm_uuid=str(remote_realm.uuid),
+        remote_billing_user_id=None,
         authenticated_at=datetime_to_timestamp(timezone_now()),
         uri_scheme=uri_scheme,
         next_page=next_page,
@@ -100,14 +102,34 @@ def remote_realm_billing_entry(
     return json_success(request, data={"billing_access_url": billing_access_url})
 
 
+def get_identity_dict_from_signed_access_token(
+    signed_billing_access_token: str,
+) -> RemoteBillingIdentityDict:
+    try:
+        identity_dict: RemoteBillingIdentityDict = signing.loads(
+            signed_billing_access_token,
+            max_age=REMOTE_BILLING_SIGNED_ACCESS_TOKEN_VALIDITY_IN_SECONDS,
+        )
+    except signing.SignatureExpired:
+        raise JsonableError(_("Billing access token expired."))
+    except signing.BadSignature:
+        raise JsonableError(_("Invalid billing access token."))
+    return identity_dict
+
+
 @self_hosting_management_endpoint
 @typed_endpoint
 def remote_realm_billing_finalize_login(
     request: HttpRequest,
     *,
     signed_billing_access_token: PathOnly[str],
+    full_name: Optional[str] = None,
     tos_consent: Literal[None, "true"] = None,
 ) -> HttpResponse:
+    """
+    This is the endpoint accessed via the billing_access_url, generated by
+    remote_realm_billing_entry entry.
+    """
     if request.method not in ["GET", "POST"]:
         return HttpResponseNotAllowed(["GET", "POST"])
     tos_consent_given = tos_consent == "true"
@@ -118,23 +140,19 @@ def remote_realm_billing_finalize_login(
         <= REMOTE_BILLING_SESSION_VALIDITY_SECONDS
     )
 
-    try:
+    identity_dict = get_identity_dict_from_signed_access_token(signed_billing_access_token)
-        identity_dict: RemoteBillingIdentityDict = signing.loads(
-            signed_billing_access_token,
-            max_age=REMOTE_BILLING_SIGNED_ACCESS_TOKEN_VALIDITY_IN_SECONDS,
-        )
-    except signing.SignatureExpired:
-        raise JsonableError(_("Billing access token expired."))
-    except signing.BadSignature:
-        raise JsonableError(_("Invalid billing access token."))
 
-    # Now we want to fetch (or create) the RemoteRealmBillingUser object implied
+    # Now we want to fetch the RemoteRealmBillingUser object implied
     # by the IdentityDict. We'll use this:
     # (1) If the user came here via just GET, we want to show them a confirmation
     #     page with the relevant info details before finalizing login. If they wish
     #     to proceed, they'll approve the form, causing a POST, bring us to case (2).
     # (2) If the user came here via POST, we finalize login, using the info from the
     #     IdentityDict to update the RemoteRealmBillingUser object if needed.
+    # Finally, if the user is logging in for the first time, we'll need to create
+    # their account first. This will happen by making them fill out a form to confirm
+    # their email first. Only after clicking the confirmation link in the email,
+    # they will have their account created and finally be redirected back here.
     remote_realm_uuid = identity_dict["remote_realm_uuid"]
     remote_server_uuid = identity_dict["remote_server_uuid"]
     try:
@@ -148,7 +166,6 @@ def remote_realm_billing_finalize_login(
     user_dict = identity_dict["user"]
 
     user_email = user_dict["user_email"]
-    user_full_name = user_dict["user_full_name"]
     user_uuid = user_dict["user_uuid"]
 
     assert (
@@ -164,47 +181,71 @@ def remote_realm_billing_finalize_login(
             remote_user.tos_version.split(".")[0]
         )
     except RemoteRealmBillingUser.DoesNotExist:
-        # This is the first time this user is logging in, so ToS consent needed.
+        # This is the first time this user is logging in.
+        remote_user = None
         tos_consent_needed = True
 
     if request.method == "GET":
-        context = {
+        if remote_user is not None:
-            "remote_server_uuid": remote_server_uuid,
+            # Render a template where the user will just confirm their info,
-            "remote_realm_uuid": remote_realm_uuid,
+            # possibly accept ToS if needed, POST back here and will get fully
-            "host": remote_realm.host,
+            # authenticated.
-            "user_email": user_email,
+            context = {
-            "user_full_name": user_full_name,
+                "remote_server_uuid": remote_server_uuid,
-            "tos_consent_needed": tos_consent_needed,
+                "remote_realm_uuid": remote_realm_uuid,
-            "action_url": reverse(
+                "host": remote_realm.host,
-                remote_realm_billing_finalize_login, args=(signed_billing_access_token,)
+                "user_email": remote_user.email,
-            ),
+                "user_full_name": remote_user.full_name,
-        }
+                "tos_consent_needed": tos_consent_needed,
-        return render(
+                "action_url": reverse(
-            request,
+                    remote_realm_billing_finalize_login, args=(signed_billing_access_token,)
-            "corporate/remote_realm_billing_finalize_login_confirmation.html",
+                ),
-            context=context,
+            }
-        )
+            return render(
+                request,
+                "corporate/remote_realm_billing_finalize_login_confirmation.html",
+                context=context,
+            )
+        else:
+            # This user is logging in for the first time, so we need to create their
+            # RemoteRealmBillingUser object. Render a template where they'll
+            # enter their email address - we'll send a verification email to it.
+            context = {
+                "email": user_email,
+                "action_url": reverse(
+                    remote_realm_billing_confirm_email, args=(signed_billing_access_token,)
+                ),
+            }
+            return render(
+                request,
+                # TODO: We're re-using a template originally made for the legacy server
+                # flow. We should rename it and its HTML contents to a more general name.
+                "corporate/remote_billing_legacy_server_confirm_login_form.html",
+                context=context,
+            )
 
     assert request.method == "POST"
+    if remote_user is None:
+        # Users logging in for the first time need to be created and follow
+        # a different path - they should not be POSTing here. It should be impossible
+        # to get here with a remote_user that is None without tampering with the form
+        # or manualling crafting a POST request.
+        raise JsonableError(_("User account doesn't exist yet."))
 
     if tos_consent_needed and not tos_consent_given:
         # This shouldn't be possible without tampering with the form, so we
         # don't need a pretty error.
         raise JsonableError(_("You must accept the Terms of Service to proceed."))
 
-    remote_user, created = RemoteRealmBillingUser.objects.get_or_create(
+    # The current approach is to update the full_name
-        defaults={"full_name": user_full_name, "email": user_email},
+    # based on what the user entered in the login confirmation form.
-        remote_realm=remote_realm,
+    # Usually they'll presumably just use the name already set for this object.
-        user_uuid=user_uuid,
+    if full_name is not None:
-    )
+        remote_user.full_name = full_name
-
-    # The current approach is to just update the email and full_name
-    # based on the info provided by the remote server during auth.
-    remote_user.email = user_email
-    remote_user.full_name = user_full_name
     remote_user.tos_version = settings.TERMS_OF_SERVICE_VERSION
-    remote_user.save(update_fields=["email", "full_name", "tos_version"])
+    remote_user.save(update_fields=["full_name", "tos_version"])
 
+    identity_dict["remote_billing_user_id"] = remote_user.id
     request.session["remote_billing_identities"] = {}
     request.session["remote_billing_identities"][
         f"remote_realm:{remote_realm_uuid}"
@@ -224,6 +265,150 @@ def remote_realm_billing_finalize_login(
         )
 
 
+@self_hosting_management_endpoint
+@typed_endpoint
+def remote_realm_billing_confirm_email(
+    request: HttpRequest,
+    *,
+    signed_billing_access_token: PathOnly[str],
+    email: str,
+) -> HttpResponse:
+    """
+    Endpoint for users in the RemoteRealm flow that are logging in for the first time
+    and still have to have their RemoteRealmBillingUser object created.
+    Takes the POST from the above form asking for their email address
+    and sends confirmation email to the provided
+    email address in order to verify. Only the confirmation link will grant
+    a fully authenticated session.
+    """
+
+    identity_dict = get_identity_dict_from_signed_access_token(signed_billing_access_token)
+    try:
+        remote_server = get_remote_server_by_uuid(identity_dict["remote_server_uuid"])
+        remote_realm = RemoteRealm.objects.get(
+            uuid=identity_dict["remote_realm_uuid"], server=remote_server
+        )
+    except ObjectDoesNotExist:
+        raise AssertionError
+
+    obj = PreregistrationRemoteRealmBillingUser.objects.create(
+        email=email,
+        remote_realm=remote_realm,
+        user_uuid=identity_dict["user"]["user_uuid"],
+        next_page=identity_dict["next_page"],
+        uri_scheme=identity_dict["uri_scheme"],
+    )
+    url = create_remote_billing_confirmation_link(
+        obj,
+        Confirmation.REMOTE_REALM_BILLING_LEGACY_LOGIN,
+        # Use the same expiration time as for the signed access token,
+        # since this is similarly transient in nature.
+        validity_in_minutes=int(REMOTE_BILLING_SIGNED_ACCESS_TOKEN_VALIDITY_IN_SECONDS / 60),
+    )
+
+    context = {
+        "remote_server_hostname": remote_server.hostname,
+        "remote_realm_host": remote_realm.host,
+        "confirmation_url": url,
+    }
+    send_email(
+        "zerver/emails/remote_realm_billing_confirm_login",
+        to_emails=[email],
+        from_address=FromAddress.tokenized_no_reply_address(),
+        context=context,
+    )
+
+    return render(
+        request,
+        "corporate/remote_billing_email_confirmation_sent.html",
+        context={"email": email},
+    )
+
+
+@self_hosting_management_endpoint
+@typed_endpoint
+def remote_realm_billing_from_login_confirmation_link(
+    request: HttpRequest,
+    *,
+    confirmation_key: PathOnly[str],
+) -> HttpResponse:
+    """
+    The user comes here via the confirmation link they received via email.
+    Creates the RemoteRealmBillingUser object and redirects to
+    remote_realm_billing_finalize_login with a new signed access token,
+    where they will finally be logged in now that they have an account.
+    """
+    try:
+        prereg_object = get_object_from_key(
+            confirmation_key,
+            [Confirmation.REMOTE_REALM_BILLING_LEGACY_LOGIN],
+            # These links aren't reusable. The user just clicks it
+            # to get their account created. Afterwards, they're not
+            # subject to the confirmation link part of the flow anymore.
+            mark_object_used=True,
+        )
+    except ConfirmationKeyError as exception:
+        return render_confirmation_key_error(request, exception)
+    assert isinstance(prereg_object, PreregistrationRemoteRealmBillingUser)
+    remote_realm = prereg_object.remote_realm
+
+    uri_scheme = prereg_object.uri_scheme
+    next_page = prereg_object.next_page
+    assert next_page in VALID_NEXT_PAGES
+    assert uri_scheme in ["http://", "https://"]
+    # Mypy is not satisfied by the above assert, so we need to cast.
+    uri_scheme = cast(Literal["http://", "https://"], uri_scheme)
+
+    remote_billing_user = RemoteRealmBillingUser.objects.create(
+        email=prereg_object.email,
+        remote_realm=remote_realm,
+        user_uuid=prereg_object.user_uuid,
+    )
+
+    identity_dict = RemoteBillingIdentityDict(
+        user=RemoteBillingUserDict(
+            user_email=remote_billing_user.email,
+            user_uuid=str(remote_billing_user.user_uuid),
+            user_full_name=remote_billing_user.full_name,
+        ),
+        remote_server_uuid=str(remote_realm.server.uuid),
+        remote_realm_uuid=str(remote_realm.uuid),
+        # This will be figured out by the next endpoint in the flow anyway.
+        remote_billing_user_id=None,
+        authenticated_at=datetime_to_timestamp(timezone_now()),
+        uri_scheme=uri_scheme,
+        next_page=next_page,
+    )
+
+    signed_identity_dict = signing.dumps(identity_dict)
+
+    return HttpResponseRedirect(
+        reverse(remote_realm_billing_finalize_login, args=[signed_identity_dict])
+    )
+
+
+def create_remote_billing_confirmation_link(
+    obj: Union[PreregistrationRemoteRealmBillingUser, PreregistrationRemoteServerBillingUser],
+    confirmation_type: int,
+    validity_in_minutes: int,
+) -> str:
+    url = create_confirmation_link(
+        obj,
+        confirmation_type,
+        validity_in_minutes=validity_in_minutes,
+        no_associated_realm_object=True,
+    )
+
+    # create_confirmation_link will create the url on the root subdomain, so we need to
+    # do a hacky approach to change it into the self hosting management subdomain.
+    new_hostname = f"{settings.SELF_HOSTING_MANAGEMENT_SUBDOMAIN}.{settings.EXTERNAL_HOST}"
+    split_url = urlsplit(url)
+    modified_url = split_url._replace(netloc=new_hostname)
+    final_url = urlunsplit(modified_url)
+
+    return final_url
+
+
 def render_tmp_remote_billing_page(
     request: HttpRequest, realm_uuid: Optional[str], server_uuid: Optional[str]
 ) -> HttpResponse:
@@ -417,26 +602,18 @@ def remote_billing_legacy_server_confirm_login(
         remote_server=remote_server,
         next_page=next_page,
     )
-    url = create_confirmation_link(
+    url = create_remote_billing_confirmation_link(
         obj,
         Confirmation.REMOTE_SERVER_BILLING_LEGACY_LOGIN,
         # Use the same expiration time as for the signed access token,
         # since this is similarly transient in nature.
         validity_in_minutes=int(REMOTE_BILLING_SIGNED_ACCESS_TOKEN_VALIDITY_IN_SECONDS / 60),
-        no_associated_realm_object=True,
     )
 
-    # create_confirmation_link will create the url on the root subdomain, so we need to
-    # do a hacky approach to change it into the self hosting management subdomain.
-    new_hostname = f"{settings.SELF_HOSTING_MANAGEMENT_SUBDOMAIN}.{settings.EXTERNAL_HOST}"
-    split_url = urlsplit(url)
-    modified_url = split_url._replace(netloc=new_hostname)
-    final_url = urlunsplit(modified_url)
-
     context = {
         "remote_server_hostname": remote_server.hostname,
         "remote_server_uuid": str(remote_server.uuid),
-        "confirmation_url": final_url,
+        "confirmation_url": url,
     }
     send_email(
         "zerver/emails/remote_billing_legacy_server_confirm_login",
@@ -447,7 +624,7 @@ def remote_billing_legacy_server_confirm_login(
 
     return render(
         request,
-        "corporate/remote_billing_legacy_server_confirm_login_sent.html",
+        "corporate/remote_billing_email_confirmation_sent.html",
         context={"email": email},
     )
 

templates/corporate/remote_billing_legacy_server_confirm_login_form.html

@@ -21,7 +21,7 @@
                 {% endif %}
                 <div class="input-box server-login-form-field">
                     <label for="email" class="inline-block label-title">Email</label>
-                    <input id="email" name="email" class="email required" type="email" />
+                    <input id="email" name="email" class="email required" type="email" {% if email %}value="{{ email }}"{% endif %} />
                 </div>
                 <div class="upgrade-button-container">
                     <button type="submit" id="server-confirm-login-button" class="stripe-button-el invoice-button">

templates/corporate/remote_realm_billing_finalize_login_confirmation.html

@@ -14,18 +14,13 @@
         <div class="white-box">
             <p>Click <b>Continue</b> to log in to Zulip server
             billing with the account below.</p>
-            {% if not legacy_server_confirmation_flow %}
-            Full name: {{ user_full_name }}<br />
-            {% endif %}
             Email: {{ user_email }}<br />
             <form id="remote-realm-confirm-login-form" method="post" action="{{ action_url }}">
                 {{ csrf_input }}
-                {% if legacy_server_confirmation_flow %}
                 <div class="input-box remote-realm-confirm-login-form-field">
                     <label for="full_name" class="inline-block label-title">Full name</label>
-                    <input id="full_name" name="full_name" class="required" type="text"/>
+                    <input id="full_name" name="full_name" class="required" type="text" {% if user_full_name %}value="{{ user_full_name }}"{% endif %} />
                 </div>
-                {% endif %}
                 {% if tos_consent_needed %}
                 <div class="input-group terms-of-service">
                     <label for="id_terms" class="inline-block checkbox">

templates/zerver/emails/remote_realm_billing_confirm_login.html

@@ -0,0 +1,22 @@
+{% extends "zerver/emails/email_base_default.html" %}
+
+{% block illustration %}
+<img src="{{ email_images_base_url }}/registration_confirmation.png" alt=""/>
+{% endblock %}
+
+{% block content %}
+<p>
+    {{ _("You have initiated login to the Zulip plan management system for the following organization:") }}
+    <ul>
+        <li>{% trans %}Organization host: {{ remote_realm_host }}{% endtrans %}</li>
+        <li>{% trans %}Server host: {{ remote_server_hostname }}{% endtrans %}</li>
+    </ul>
+</p>
+<p>
+    {{ _("Click the button below to complete the login process.") }}
+    <a class="button" href="{{ confirmation_url }}">{{ _("Confirm login") }}</a>
+</p>
+<p>
+    {{macros.contact_us_zulip_cloud(support_email)}}
+</p>
+{% endblock %}

templates/zerver/emails/remote_realm_billing_confirm_login.subject.txt

@@ -0,0 +1 @@
+{% trans %}Confirm login to Zulip plan management{% endtrans %}

templates/zerver/emails/remote_realm_billing_confirm_login.txt

@@ -0,0 +1,9 @@
+{{ _("You have initiated login to the Zulip plan management system for the following organization:") }}
+* {% trans %}Organization host: {{ remote_realm_host }}{% endtrans %}
+
+* {% trans %}Server host: {{ remote_server_hostname }}{% endtrans %}
+
+{{ _("Click the link below to complete the login process;") }}
+    <{{ confirmation_url }}>
+
+{% trans %}Do you have questions or feedback to share? Contact us at {{ support_email }} — we'd love to help!{% endtrans %}

tools/lib/capitalization.py

@@ -239,7 +239,11 @@ def check_banned_words(text: str) -> List[str]:
         if word in lower_cased_text:
             # Hack: Should move this into BANNED_WORDS framework; for
             # now, just hand-code the skips:
-            if "realm_name" in lower_cased_text or "realm_uri" in lower_cased_text:
+            if (
+                "realm_name" in lower_cased_text
+                or "realm_uri" in lower_cased_text
+                or "remote_realm_host" in lower_cased_text
+            ):
                 continue
             kwargs = dict(word=word, text=text, reason=reason)
             msg = "{word} found in '{text}'. {reason}".format(**kwargs)

zilencer/migrations/0049_alter_remoterealmbillinguser_unique_together_and_more.py

@@ -0,0 +1,42 @@
+# Generated by Django 4.2.8 on 2023-12-10 01:01
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zilencer", "0048_remotezulipserver_last_api_feature_level"),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name="remoterealmbillinguser",
+            unique_together={("remote_realm", "user_uuid")},
+        ),
+        migrations.CreateModel(
+            name="PreregistrationRemoteRealmBillingUser",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True, primary_key=True, serialize=False, verbose_name="ID"
+                    ),
+                ),
+                ("user_uuid", models.UUIDField()),
+                ("email", models.EmailField(max_length=254)),
+                ("status", models.IntegerField(default=0)),
+                ("next_page", models.TextField(null=True)),
+                ("uri_scheme", models.TextField()),
+                (
+                    "remote_realm",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE, to="zilencer.remoterealm"
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+    ]

zilencer/models.py

@@ -154,17 +154,40 @@ class RemoteRealm(models.Model):
         return f"{self.host} {str(self.uuid)[0:12]}"
 
 
-class RemoteRealmBillingUser(models.Model):
+class AbstractRemoteRealmBillingUser(models.Model):
     remote_realm = models.ForeignKey(RemoteRealm, on_delete=models.CASCADE)
 
     # The .uuid of the UserProfile on the remote server
     user_uuid = models.UUIDField()
-    full_name = models.TextField(default="")
     email = models.EmailField()
 
+    class Meta:
+        abstract = True
+
+
+class RemoteRealmBillingUser(AbstractRemoteRealmBillingUser):
+    full_name = models.TextField(default="")
+
     TOS_VERSION_BEFORE_FIRST_LOGIN = UserProfile.TOS_VERSION_BEFORE_FIRST_LOGIN
     tos_version = models.TextField(default=TOS_VERSION_BEFORE_FIRST_LOGIN)
 
+    class Meta:
+        unique_together = [
+            ("remote_realm", "user_uuid"),
+        ]
+
+
+class PreregistrationRemoteRealmBillingUser(AbstractRemoteRealmBillingUser):
+    # status: whether an object has been confirmed.
+    #   if confirmed, set to confirmation.settings.STATUS_USED
+    status = models.IntegerField(default=0)
+
+    # These are for carrying certain information that's originally
+    # in an IdentityDict across the confirmation link flow. These
+    # values will be restored in the final, fully authenticated IdentityDict.
+    next_page = models.TextField(null=True)
+    uri_scheme = models.TextField()
+
 
 class AbstractRemoteServerBillingUser(models.Model):
     remote_server = models.ForeignKey(RemoteZulipServer, on_delete=models.CASCADE)