Make sure we use the right logic for enabling the media repo. (#17424)

This removes the `enable_media_repo` attribute on the server config in
favour of always using the `can_load_media_repo` in the media config.
This should avoid issues like in #17420 in the future

changelog.d/17424.misc

@@ -0,0 +1 @@
+Make sure we always use the right logic for enabling the media repo.

synapse/app/homeserver.py

@@ -217,7 +217,7 @@ def _configure_named_resource(
             )
 
         if name in ["media", "federation", "client"]:
-            if self.config.server.enable_media_repo:
+            if self.config.media.can_load_media_repo:
                 media_repo = self.get_media_repository_resource()
                 resources.update(
                     {

synapse/config/repository.py

@@ -126,7 +126,7 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         # Only enable the media repo if either the media repo is enabled or the
         # current worker app is the media repo.
         if (
-            self.root.server.enable_media_repo is False
+            config.get("enable_media_repo", True) is False
             and config.get("worker_app") != "synapse.app.media_repository"
         ):
             self.can_load_media_repo = False

synapse/config/server.py

@@ -395,12 +395,6 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
                 self.presence_router_config,
             ) = load_module(presence_router_config, ("presence", "presence_router"))
 
-        # whether to enable the media repository endpoints. This should be set
-        # to false if the media repository is running as a separate endpoint;
-        # doing so ensures that we will not run cache cleanup jobs on the
-        # master, potentially causing inconsistency.
-        self.enable_media_repo = config.get("enable_media_repo", True)
-
         # Whether to require authentication to retrieve profile data (avatars,
         # display names) of other users through the client API.
         self.require_auth_for_profile_requests = config.get(