请求地址：https://api.mch.weixin.qq.com/pay/downloadbill

支付请求attach入参：{"orderType":1,"orderId":"SP20250516174050074531919","tenantId":1,"env":"dev"}

下载请求attach响应内容为：{\"orderType\":1\ \"orderId\":\"SP20250516174050074531919\"\ \"tenantId\":1\ \"env\":\"dev\"}