商户后台：
https://hmpay.sandpay.com.cn/merchant/login

河马付交易请求地址：
https://hmpay.sandpay.com.cn/gateway/api



河马付产品接入指南：
https://sand.yuque.com/docs/share/f5840d84-08a3-409d-8ab9-854d30562660

https://sand.yuque.com/hmkf/hmpay/tywgjk


河马付新收银台（含APP接入SDK/H5）：
https://www.yuque.com/docs/share/a92a7612-4a49-4189-9807-840e58bf9b77


河马付统一预下单（JSAPI）：
https://sand.yuque.com/hmkf/hmpay/tywgjk#6GLo7
https://sand.yuque.com/hmkf/itc5qg/gc2hl5#6GLo7