Clean up `Notifier.on_new_room_event` code path (#8288)

The idea here is that we pass the `max_stream_id` to everything, and only use the stream ID of the particular event to figure out *when* the max stream position has caught up to the event and we can notify people about it.

This is to maintain the distinction between the position of an item in the stream (i.e. event A has stream ID 513) and a token that can be used to partition the stream (i.e. give me all events after stream ID 352). This distinction becomes important when the tokens are more complicated than a single number, which they will be once we start tracking the position of multiple writers in the tokens.

The valid operations here are:

1. Is a position before or after a token
2. Fetching all events between two tokens
3. Merging multiple tokens to get the "max", i.e. `C = max(A, B)` means that for all positions P where P is before A *or* before B, then P is before C.

Future PR will change the token type to a dedicated type.

1 files changed, 1 insertions, 1 deletions

diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py
index fa8473bf8d..cc839ffce4 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -184,7 +184,7 @@ class PusherPool:
                 )
                 await self.remove_pusher(p["app_id"], p["pushkey"], p["user_name"])
 
-    async def on_new_notifications(self, max_stream_id):
+    async def on_new_notifications(self, max_stream_id: int):
         if not self.pushers:
             # nothing to do here.
             return