demo-orgs: Set owner `email_address_visibility` on account creation.

Since an email address is not required to create a demo organization,
we need a Zulip API email address for the web-app to use until the
owner configures an email for their account.

Here, we set the owner's `email_address_visibility` to "Nobody" when
the owner's account is created so that the Zulip API email field in
their profile is a fake email address string.

zerver/tests/test_signup.py

@@ -3957,6 +3957,11 @@ class UserSignUpTest(ZulipTestCase):
         scheduled_email = ScheduledEmail.objects.filter(users=user_profile).last()
         assert scheduled_email is None
 
+        self.assertIn(realm.string_id, user_profile.email)
+        self.assertEqual(
+            user_profile.email_address_visibility, UserProfile.EMAIL_ADDRESS_VISIBILITY_NOBODY
+        )
+
         expected_deletion_date = realm.date_created + datetime.timedelta(
             days=settings.DEMO_ORG_DEADLINE_DAYS
         )

zerver/views/development/registration.py

@@ -94,6 +94,7 @@ def register_demo_development_realm(request: HttpRequest) -> HttpResponse:
     realm_name = generate_demo_realm_name()
     realm_type = Realm.ORG_TYPES["business"]["id"]
     realm_subdomain = realm_name
+    email_address_visibility = UserProfile.EMAIL_ADDRESS_VISIBILITY_NOBODY
     prereg_realm = create_preregistration_realm(email, realm_name, realm_subdomain, realm_type)
     activation_url = create_confirmation_link(
         prereg_realm, Confirmation.REALM_CREATION, realm_creation=True
@@ -105,6 +106,7 @@ def register_demo_development_realm(request: HttpRequest) -> HttpResponse:
         key=key,
         realm_name=realm_name,
         realm_type=realm_type,
+        email_address_visibility=email_address_visibility,
         full_name=name,
         password="test",
         realm_subdomain=realm_subdomain,