billing: Enforce manual billing renewal licenses for new users.

In addition to checking for available licenses in the current
billing period when adding or inviting new non-guest users, for
manual billing, we also verify that the number of licenses set
for the next billing period will be enough when adding/inviting
new users.

Realms that are exempt from license number checks do not have
this restriction applied.

Admins are notified via group direct message when a user fails
to register due to this restriction.

corporate/lib/registration.py

@@ -60,13 +60,13 @@ def send_user_unable_to_signup_group_direct_message_to_admins(
     realm: Realm, user_email: str
 ) -> None:
     message = _(
-        "A new member ({email}) was unable to join your organization because all Zulip licenses "
-        "are in use. Please [increase the number of licenses]({billing_page_link}) or "
-        "[deactivate inactive users]({deactivate_user_help_page_link}) to allow new members to join."
+        "A new user ({email}) was unable to join because your organization does not have enough "
+        "Zulip licenses. To allow new users to join, make sure that the [number of licenses for "
+        "the current and next billing period]({billing_page_link}) is greater than the current "
+        "number of users."
     ).format(
         email=user_email,
         billing_page_link="/billing/",
-        deactivate_user_help_page_link="/help/deactivate-or-reactivate-a-user",
     )
 
     send_group_direct_message_to_admins(
@@ -77,9 +77,12 @@ def send_user_unable_to_signup_group_direct_message_to_admins(
 def check_spare_licenses_available(
     realm: Realm, plan: CustomerPlan, extra_non_guests_count: int = 0, extra_guests_count: int = 0
 ) -> None:
-    if plan.licenses() < get_seat_count(
+    seat_count = get_seat_count(
         realm, extra_non_guests_count=extra_non_guests_count, extra_guests_count=extra_guests_count
-    ):
+    )
+    current_licenses = plan.licenses()
+    renewal_licenses = plan.licenses_at_next_renewal()
+    if current_licenses < seat_count or (renewal_licenses and renewal_licenses < seat_count):
         raise LicenseLimitError
 
 
@@ -105,7 +108,6 @@ def check_spare_licenses_available_for_registering_new_user(
 def check_spare_licenses_available_for_inviting_new_users(
     realm: Realm, extra_non_guests_count: int = 0, extra_guests_count: int = 0
 ) -> None:
-    num_invites = extra_non_guests_count + extra_guests_count
     plan = get_plan_if_manual_license_management_enforced(realm)
     if plan is None:
         return
@@ -113,10 +115,7 @@ def check_spare_licenses_available_for_inviting_new_users(
     try:
         check_spare_licenses_available(realm, plan, extra_non_guests_count, extra_guests_count)
     except LicenseLimitError:
-        if num_invites == 1:
-            message = _("All Zulip licenses for this organization are currently in use.")
-        else:
-            message = _(
-                "Your organization does not have enough unused Zulip licenses to invite {num_invites} users."
-            ).format(num_invites=num_invites)
+        message = _(
+            "Your organization does not have enough Zulip licenses. Invitations were not sent."
+        )
         raise InvitationError(message, [], sent_invitations=False, license_limit_reached=True)

zerver/tests/test_invite.py

@@ -535,19 +535,24 @@ class InviteUserTest(InviteUserBase):
             result = self.invite(self.nonreg_email("alice"), ["Denmark"])
         self.assert_json_success(result)
 
-        ledger.licenses_at_next_renewal = 5
+        ledger.licenses_at_next_renewal = get_latest_seat_count(user.realm)
         ledger.save(update_fields=["licenses_at_next_renewal"])
         with self.settings(BILLING_ENABLED=True):
             result = self.invite(self.nonreg_email("bob"), ["Denmark"])
-        self.assert_json_success(result)
+        self.assert_json_error_contains(
+            result,
+            "Your organization does not have enough Zulip licenses. Invitations were not sent.",
+        )
 
+        ledger.licenses_at_next_renewal = 50
         ledger.licenses = get_latest_seat_count(user.realm) + 1
-        ledger.save(update_fields=["licenses"])
+        ledger.save(update_fields=["licenses", "licenses_at_next_renewal"])
         with self.settings(BILLING_ENABLED=True):
             invitee_emails = self.nonreg_email("bob") + "," + self.nonreg_email("alice")
             result = self.invite(invitee_emails, ["Denmark"])
         self.assert_json_error_contains(
-            result, "Your organization does not have enough unused Zulip licenses to invite 2 users"
+            result,
+            "Your organization does not have enough Zulip licenses. Invitations were not sent.",
         )
 
         ledger.licenses = get_latest_seat_count(user.realm)
@@ -555,7 +560,8 @@ class InviteUserTest(InviteUserBase):
         with self.settings(BILLING_ENABLED=True):
             result = self.invite(self.nonreg_email("bob"), ["Denmark"])
         self.assert_json_error_contains(
-            result, "All Zulip licenses for this organization are currently in use"
+            result,
+            "Your organization does not have enough Zulip licenses. Invitations were not sent.",
         )
 
         with self.settings(BILLING_ENABLED=True):

zerver/tests/test_signup.py

@@ -3026,7 +3026,7 @@ class UserSignUpTest(ZulipTestCase):
             last_message = Message.objects.last()
             assert last_message is not None
             self.assertIn(
-                f"A new member ({self.nonreg_email('test')}) was unable to join your organization because all Zulip",
+                f"A new user ({self.nonreg_email('test')}) was unable to join because your organization",
                 last_message.content,
             )
             self.assertEqual(
@@ -3044,7 +3044,27 @@ class UserSignUpTest(ZulipTestCase):
             )
 
         ledger.licenses = 50
-        ledger.save(update_fields=["licenses"])
+        ledger.licenses_at_next_renewal = 5
+        ledger.save(update_fields=["licenses", "licenses_at_next_renewal"])
+        with self.settings(BILLING_ENABLED=True):
+            form = HomepageForm({"email": self.nonreg_email("test")}, realm=realm)
+            self.assertIn(
+                "New members cannot join this organization because all Zulip licenses",
+                form.errors["email"][0],
+            )
+            last_message = Message.objects.last()
+            assert last_message is not None
+            self.assertIn(
+                f"A new user ({self.nonreg_email('test')}) was unable to join because your organization",
+                last_message.content,
+            )
+            self.assertEqual(
+                set(get_direct_message_group_user_ids(last_message.recipient)),
+                expected_group_direct_message_user_ids,
+            )
+
+        ledger.licenses_at_next_renewal = 50
+        ledger.save(update_fields=["licenses_at_next_renewal"])
         with self.settings(BILLING_ENABLED=True):
             form = HomepageForm({"email": self.nonreg_email("test")}, realm=realm)
             self.assertEqual(form.errors, {})