public static void Unregister(IReceiveActivityLifecycleEvents listener)
        {
            var oldListener = listeners.FirstOrDefault(x => x == listener);

            if (oldListener != null)
            {
                listeners.Remove(oldListener);
            }
        }
 public static void Register(IReceiveActivityLifecycleEvents listener)
 {
     // TODO: create a replayable subscription that gets reset when OnPause/OnDestroy/OnStop are invoked
     // that way each new subscriber will receive the latest create/start/resume when they subscribe
     listeners.Add(listener);
 }