audit log: Create audit log when a realm is created.

This is mainly useful in recording the user who created the realm,
when possible.

zerver/lib/server_initialization.py

@@ -3,7 +3,7 @@ from typing import Iterable, Optional, Tuple
 from django.conf import settings
 
 from zerver.lib.bulk_create import bulk_create_users
-from zerver.models import Realm, UserProfile, get_client, get_system_bot
+from zerver.models import Realm, RealmAuditLog, UserProfile, get_client, get_system_bot
 
 
 def server_initialized() -> bool:
@@ -14,6 +14,9 @@ def create_internal_realm() -> None:
     from zerver.lib.actions import do_change_can_forge_sender
 
     realm = Realm.objects.create(string_id=settings.SYSTEM_BOT_REALM)
+    RealmAuditLog.objects.create(
+        realm=realm, event_type=RealmAuditLog.REALM_CREATED, event_time=realm.date_created
+    )
 
     # Create some client objects for common requests.  Not required;
     # just ensures these get low IDs in production, and in development