官方文档:https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/login/auth.code2Session.html
// 获取 session_key,返回数组
$result = $app->auth->session($code)官方文档:https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/login/auth.code2Session.html
// 获取 session_key,返回数组
$result = $app->auth->session($code)