do_delete_user: Use get_fake_email_domain for dummy user email domain.

Otherwise the dummy user can be created with an invalid email domain -
e.g. in development environment with the domain
"@http://localhost:9991". get_fake_email_domain exists exactly for
handling these kinds of scenarios.

zerver/lib/actions.py

@@ -239,6 +239,7 @@ from zerver.models import (
     get_bot_services,
     get_client,
     get_default_stream_groups,
+    get_fake_email_domain,
     get_huddle_recipient,
     get_huddle_user_ids,
     get_old_unclaimed_attachments,
@@ -1224,7 +1225,7 @@ def do_delete_user(user_profile: UserProfile) -> None:
     personal_recipient.delete()
     replacement_user = create_user(
         force_id=user_id,
-        email=f"deleteduser{user_id}@{realm.uri}",
+        email=f"deleteduser{user_id}@{get_fake_email_domain(realm)}",
         password=None,
         realm=realm,
         full_name=f"Deleted User {user_id}",

zerver/tests/test_users.py

@@ -2068,7 +2068,7 @@ class DeleteUserTest(ZulipTestCase):
         replacement_dummy_user = UserProfile.objects.get(id=hamlet_user_id, realm=realm)
 
         self.assertEqual(
-            replacement_dummy_user.delivery_email, f"deleteduser{hamlet_user_id}@{realm.uri}"
+            replacement_dummy_user.delivery_email, f"deleteduser{hamlet_user_id}@zulip.testserver"
         )
         self.assertEqual(replacement_dummy_user.is_mirror_dummy, True)
         self.assertEqual(replacement_dummy_user.is_active, False)