Add userFlagged subscription

graph/typeDefs.graphql

@@ -1506,6 +1506,11 @@ type Subscription {
   # users with the `ADMIN` or `MODERATOR` role.
   userBanned(user_id: ID): User
 
+  # Get an update whenever a username was flagged.
+  # `user_id` must match id of current user except for
+  # users with the `ADMIN` or `MODERATOR` role.
+  usernameFlagged(user_id: ID): User
+
   # Get an update whenever a username has been rejected.
   # `user_id` must match id of current user except for
   # users with the `ADMIN` or `MODERATOR` role.