Make a fake requester with just what we need

See https://github.com/matrix-org/synapse/pull/10276#discussion_r660999080

synapse/rest/client/v1/room.py

@@ -47,12 +47,12 @@ from synapse.storage.state import StateFilter
 from synapse.streams.config import PaginationConfig
 from synapse.types import (
     JsonDict,
-    Requester,
     RoomAlias,
     RoomID,
     StreamToken,
     ThirdPartyInstanceID,
     UserID,
+    create_requester,
 )
 from synapse.util import json_decoder
 from synapse.util.stringutils import parse_and_validate_server_name, random_string
@@ -310,13 +310,6 @@ class RoomBatchSendEventRestServlet(TransactionRestServlet):
         self.room_member_handler = hs.get_room_member_handler()
         self.auth = hs.get_auth()
 
-    def _copy_requester_and_override_user_id(self, requester, new_user_id):
-        serialized_requester = requester.serialize()
-        serialized_requester["user_id"] = new_user_id
-        new_requester = Requester.deserialize(self.store, serialized_requester)
-
-        return new_requester
-
     async def _inherit_depth_from_prev_ids(self, prev_event_ids) -> int:
         (
             most_recent_prev_event_id,
@@ -447,8 +440,8 @@ class RoomBatchSendEventRestServlet(TransactionRestServlet):
             if event_dict["type"] == EventTypes.Member:
                 membership = event_dict["content"].get("membership", None)
                 event_id, _ = await self.room_member_handler.update_membership(
-                    self._copy_requester_and_override_user_id(
-                        requester, state_event["sender"]
+                    create_requester(
+                        state_event["sender"], app_service=requester.app_service
                     ),
                     target=UserID.from_string(event_dict["state_key"]),
                     room_id=room_id,
@@ -469,8 +462,8 @@ class RoomBatchSendEventRestServlet(TransactionRestServlet):
                     event,
                     _,
                 ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                    self._copy_requester_and_override_user_id(
-                        requester, state_event["sender"]
+                    create_requester(
+                        state_event["sender"], app_service=requester.app_service
                     ),
                     event_dict,
                     outlier=True,
@@ -552,7 +545,7 @@ class RoomBatchSendEventRestServlet(TransactionRestServlet):
             }
 
             event, context = await self.event_creation_handler.create_event(
-                self._copy_requester_and_override_user_id(requester, ev["sender"]),
+                create_requester(ev["sender"], app_service=requester.app_service),
                 event_dict,
                 prev_event_ids=event_dict.get("prev_events"),
                 auth_event_ids=auth_event_ids,
@@ -582,7 +575,7 @@ class RoomBatchSendEventRestServlet(TransactionRestServlet):
         # where topological_ordering is just depth.
         for (event, context) in reversed(events_to_persist):
             ev = await self.event_creation_handler.handle_new_client_event(
-                self._copy_requester_and_override_user_id(requester, event["sender"]),
+                create_requester(event["sender"], app_service=requester.app_service),
                 event=event,
                 context=context,
             )