feat(miniapp): 小程序订阅消息 (#429)

1. 用户订阅消息服务端回调处理
2. 用户订阅消息订阅通知事件推送

Co-authored-by: houseme <qzg40737@163.com>

miniprogram/message/reply.go

@@ -0,0 +1,15 @@
+package message
+
+import "errors"
+
+//ErrInvalidReply 无效的回复
+var ErrInvalidReply = errors.New("无效的回复信息")
+
+//ErrUnsupportedReply 不支持的回复类型
+var ErrUnsupportedReply = errors.New("不支持的回复消息")
+
+//Reply 消息回复
+type Reply struct {
+	MsgType MsgType
+	MsgData interface{}
+}