Return a room's current join_rule in each public rooms list entry

Author: anoadragon453

synapse/handlers/room_list.py

@@ -169,6 +169,7 @@ def build_room_entry(room):
                 "world_readable": room["history_visibility"]
                 == HistoryVisibility.WORLD_READABLE,
                 "guest_can_join": room["guest_access"] == "can_join",
+                "join_rule": room["join_rules"],
             }
 
             # Filter out Nones – rather omit the field altogether

synapse/storage/databases/main/room.py

@@ -305,7 +305,7 @@ async def get_largest_public_rooms(
         sql = """
             SELECT
                 room_id, name, topic, canonical_alias, joined_members,
-                avatar, history_visibility, joined_members, guest_access
+                avatar, history_visibility, guest_access, join_rules
             FROM (
                 %(published_sql)s
             ) published