Refactor checking restricted join rules (#10007)

To be more consistent with similar code. The check now automatically
raises an AuthError instead of passing back a boolean. It also absorbs
some shared logic between callers.

synapse/handlers/federation.py

@@ -1668,28 +1668,17 @@ class FederationHandler(BaseHandler):
         # Check if the user is already in the room or invited to the room.
         user_id = event.state_key
         prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)
-        newly_joined = True
-        user_is_invited = False
+        prev_member_event = None
         if prev_member_event_id:
             prev_member_event = await self.store.get_event(prev_member_event_id)
-            newly_joined = prev_member_event.membership != Membership.JOIN
-            user_is_invited = prev_member_event.membership == Membership.INVITE
 
-        # If the member is not already in the room, and not invited, check if
-        # they should be allowed access via membership in a space.
-        if (
-            newly_joined
-            and not user_is_invited
-            and not await self._event_auth_handler.can_join_without_invite(
-                prev_state_ids,
-                event.room_version,
-                user_id,
-            )
-        ):
-            raise AuthError(
-                403,
-                "You do not belong to any of the required spaces to join this room.",
-            )
+        # Check if the member should be allowed access via membership in a space.
+        await self._event_auth_handler.check_restricted_join_rules(
+            prev_state_ids,
+            event.room_version,
+            user_id,
+            prev_member_event,
+        )
 
         # Persist the event.
         await self._auth_and_persist_event(origin, event, context)