message: Do not include details of inaccessible users in message data.

This commit adds code to not include original details of senders like
name, email and avatar url in the message objects sent through events
and in the response of endpoint used to fetch messages.

This is the last major commit for the project to add support for
limiting guest access to an entire organization.

Fixes #10970.

zerver/tests/test_message_edit.py

@@ -55,7 +55,7 @@ class EditMessageTestCase(ZulipTestCase):
 
     def check_message(self, msg_id: int, topic_name: str, content: str) -> None:
         # Make sure we saved the message correctly to the DB.
-        msg = Message.objects.get(id=msg_id)
+        msg = Message.objects.select_related("realm").get(id=msg_id)
         self.assertEqual(msg.topic_name(), topic_name)
         self.assertEqual(msg.content, content)
 
@@ -75,6 +75,8 @@ class EditMessageTestCase(ZulipTestCase):
                 apply_markdown=False,
                 client_gravatar=False,
                 allow_edit_history=True,
+                user_profile=None,
+                realm=msg.realm,
             )
 
         self.assert_length(queries, 1)