code: private void processConversationDeliveredAt(String conversationId, int convType, long timestamp) {
      AVConversationHolder conversation = session.getConversationHolder(conversationId, convType);
      conversation.onConversationDeliveredAtEvent(timestamp);
    }
docs: 处理 v2 版本中 conversation 的 deliveredAt 事件
  @param conversationId
  @param timestamp