Allow /rooms/ admin API to be on workers (#18360)

Tested by https://github.com/matrix-org/sytest/pull/1400

changelog.d/18360.misc

@@ -0,0 +1 @@
+Allow `/rooms/` admin API to be run on workers.

docs/workers.md

@@ -249,6 +249,7 @@ information.
     ^/_matrix/client/(api/v1|r0|v3|unstable)/directory/room/.*$
     ^/_matrix/client/(r0|v3|unstable)/capabilities$
     ^/_matrix/client/(r0|v3|unstable)/notifications$
+    ^/_synapse/admin/v1/rooms/
 
     # Encryption requests
     ^/_matrix/client/(r0|v3|unstable)/keys/query$

synapse/app/generic_worker.py

@@ -52,7 +52,7 @@ from synapse.logging.context import LoggingContext
 from synapse.metrics import METRICS_PREFIX, MetricsResource, RegistryProxy
 from synapse.replication.http import REPLICATION_PREFIX, ReplicationRestResource
 from synapse.rest import ClientRestResource
-from synapse.rest.admin import register_servlets_for_media_repo
+from synapse.rest.admin import AdminRestResource, register_servlets_for_media_repo
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyResource
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
@@ -190,6 +190,7 @@ class GenericWorkerServer(HomeServer):
 
                     resources.update(build_synapse_client_resource_tree(self))
                     resources["/.well-known"] = well_known_resource(self)
+                    resources["/_synapse/admin"] = AdminRestResource(self)
 
                 elif name == "federation":
                     resources[FEDERATION_PREFIX] = TransportLayerServer(self)

synapse/rest/admin/__init__.py

@@ -275,7 +275,9 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     """
     Register all the admin servlets.
     """
-    # Admin servlets aren't registered on workers.
+    RoomRestServlet(hs).register(http_server)
+
+    # Admin servlets below may not work on workers.
     if hs.config.worker.worker_app is not None:
         return
 
@@ -283,7 +285,6 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     BlockRoomRestServlet(hs).register(http_server)
     ListRoomRestServlet(hs).register(http_server)
     RoomStateRestServlet(hs).register(http_server)
-    RoomRestServlet(hs).register(http_server)
     RoomRestV2Servlet(hs).register(http_server)
     RoomMembersRestServlet(hs).register(http_server)
     DeleteRoomStatusByDeleteIdRestServlet(hs).register(http_server)