https://developers.weixin.qq.com/doc/oplatform/Third-party_Platforms/Mini_Programs/uniform_message/uniformMessage.send.html
可以参考下这个 https://developers.weixin.qq.com/doc/oplatform/Third-party_Platforms/Mini_Programs/WeChat_login.html
https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/login/auth.code2Session.html
需用通过接口调用获得的