Wrap the "rooms" list inside an object so that we can add keys for pagination later

api/client-server/v2_alpha/sync.yaml

@@ -72,6 +72,9 @@ paths:
                   The batch token to supply in the ``since`` param of the next
                   ``/sync`` request.
               rooms:
+                type: object
+                properties:
+                  roomlist:
                     type: array
                     description: |-
                       A list of rooms that the client needs to update.
@@ -145,7 +148,8 @@ paths:
                     }
                   ]
                 },
-                "rooms": [{
+                "rooms": {
+                  "roomlist": [{
                     "room_id": "!726s6s6q:example.com",
                     "event_map": {
                       "$66697273743031:example.com": {
@@ -195,3 +199,4 @@ paths:
                     }
                   }]
                 }
+              }