message: Use .is_channel_message column instead of is_stream_message().

This avoids a potential unnecessary message.recipient fetch required by
is_stream_message(). is_stream_message() methods precedes the addition
of the denormalized is_channel_message column and is now unnecessary.

In practice, we usually fetch Message objects with `.recipient` already,
so I don't expect any notable performance impact here - but it's still a
useful change to make.

zerver/models/messages.py

@@ -283,16 +283,6 @@ class Message(AbstractMessage):
     def set_topic_name(self, topic_name: str) -> None:
         self.subject = topic_name
 
-    def is_stream_message(self) -> bool:
-        """
-        Find out whether a message is a stream message by
-        looking up its recipient.type.  TODO: Make this
-        an easier operation by denormalizing the message
-        type onto Message, either explicitly (message.type)
-        or implicitly (message.stream_id is not None).
-        """
-        return self.recipient.type == Recipient.STREAM
-
     def get_realm(self) -> Realm:
         return self.realm
 

zerver/models/scheduled_jobs.py

@@ -225,7 +225,7 @@ class ScheduledMessage(models.Model):
     def set_topic_name(self, topic_name: str) -> None:
         self.subject = topic_name
 
-    def is_stream_message(self) -> bool:
+    def is_channel_message(self) -> bool:
         return self.recipient.type == Recipient.STREAM
 
     def to_dict(self) -> APIScheduledStreamMessageDict | APIScheduledDirectMessageDict: