Disable groups/communities by default. (#12344)

This disables the endpoints (and sync response fields) for
groups/communities by default.

changelog.d/12344.removal

@@ -0,0 +1 @@
+The groups/communities feature in Synapse has been disabled by default.

docs/upgrade.md

@@ -85,6 +85,13 @@ process, for example:
     dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
     ```
 
+# Upgrading to v1.58.0
+
+## Groups/communities feature has been disabled by default
+
+The non-standard groups/communities feature in Synapse has been disabled by default
+and will be removed in Synapse v1.61.0.
+
 # Upgrading to v1.57.0
 
 ## Changes to database schema for application services

synapse/config/experimental.py

@@ -74,7 +74,7 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         self.msc3720_enabled: bool = experimental.get("msc3720_enabled", False)
 
         # The deprecated groups feature.
-        self.groups_enabled: bool = experimental.get("groups_enabled", True)
+        self.groups_enabled: bool = experimental.get("groups_enabled", False)
 
         # MSC2654: Unread counts
         self.msc2654_enabled: bool = experimental.get("msc2654_enabled", False)

tests/rest/admin/test_admin.py

@@ -63,6 +63,7 @@ def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.other_user = self.register_user("user", "pass")
         self.other_user_token = self.login("user", "pass")
 
+    @unittest.override_config({"experimental_features": {"groups_enabled": True}})
     def test_delete_group(self) -> None:
         # Create a new group
         channel = self.make_request(