Check for space membership during a remote join of a restricted room. (#9763)

When receiving a /send_join request for a room with join rules set to 'restricted',
check if the user is a member of the spaces defined in the 'allow' key of the join
rules.
    
This only applies to an experimental room version, as defined in MSC3083.

tests/test_federation.py

@@ -75,8 +75,10 @@ class MessageAcceptTests(unittest.HomeserverTestCase):
         )
 
         self.handler = self.homeserver.get_federation_handler()
-        self.handler.do_auth = lambda origin, event, context, auth_events: succeed(
-            context
+        self.handler._check_event_auth = (
+            lambda origin, event, context, state, auth_events, backfilled: succeed(
+                context
+            )
         )
         self.client = self.homeserver.get_federation_client()
         self.client._check_sigs_and_hash_and_fetch = lambda dest, pdus, **k: succeed(