https://developers.weixin.qq.com/doc/service/guide/h5/auth.html 公众号绑定了微信开放平台，appid: wxf59def6d1b7f60b3 但是，调用接口“https://api.weixin.qq.com/sns/oauth2/access_token” 返回信息WechatCode2SessionRepDto{sessionKey='null', openid='oXwUi5_FaKUxTpHYF6dxqWoLhdsc', unionid='null', errcode='null', errmsg='null'} 没有unionid