Add proper state and state_groups so historical events return state from /context

See https://gitlab.com/gitterHQ/webapp/-/merge_requests/2229#note_683532091

Also seems to fix https://github.com/matrix-org/synapse/issues/10764

synapse/handlers/message.py

@@ -959,7 +959,15 @@ class EventCreationHandler:
             event.internal_metadata.outlier = True
             context = EventContext.for_outlier()
         else:
-            context = await self.state.compute_event_context(event)
+            old_state = None
+            # Define the state for historical messages while we know to get all of
+            # state_groups setup properly when we `compute_event_context`.
+            if builder.internal_metadata.is_historical() and auth_event_ids:
+                old_state = await self.store.get_events_as_list(auth_event_ids)
+
+            context = await self.state.compute_event_context(event, old_state=old_state)
+
+        logger.info("create_new_client_event type=%s, event_id=%s context=%s", event.type, event.event_id, context)
 
         if requester:
             context.app_service = requester.app_service

synapse/rest/client/room_batch.py

@@ -176,6 +176,8 @@ class RoomBatchSendEventRestServlet(RestServlet):
     async def on_POST(
         self, request: SynapseRequest, room_id: str
     ) -> Tuple[int, JsonDict]:
+        logger.info("room batch send =====================================================")
+        logger.info("=====================================================================")
         requester = await self.auth.get_user_by_req(request, allow_guest=False)
 
         if not requester.app_service: