development: Redirect rather than mutate in register_development_user.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/views/development/registration.py

@@ -3,13 +3,12 @@ import string
 from typing import Any
 
 from django.conf import settings
-from django.http import HttpRequest, HttpResponse
+from django.http import HttpRequest, HttpResponse, HttpResponseRedirect
 from django.views.decorators.csrf import csrf_exempt
 
 from confirmation.models import Confirmation, create_confirmation_link
 from zerver.context_processors import get_realm_from_request
 from zerver.lib.response import json_success
-from zerver.lib.subdomains import get_subdomain
 from zerver.models import Realm, UserProfile
 from zerver.views.auth import create_preregistration_user
 from zerver.views.registration import accounts_register
@@ -36,12 +35,16 @@ def generate_demo_realm_name() -> str:
 
 @csrf_exempt
 def register_development_user(request: HttpRequest) -> HttpResponse:
-    if get_subdomain(request) == "":
-        request.META["HTTP_HOST"] = settings.REALM_HOSTS["zulip"]
+    realm = get_realm_from_request(request)
+    if realm is None:
+        return HttpResponseRedirect(
+            f"{settings.EXTERNAL_URI_SCHEME}{settings.REALM_HOSTS['zulip']}/devtools/register_user/",
+            status=307,
+        )
+
     count = UserProfile.objects.count()
     name = f"user-{count}"
     email = f"{name}@zulip.com"
-    realm = get_realm_from_request(request)
     prereg = create_preregistration_user(
         email, realm, realm_creation=False, password_required=False
     )