POST /api/payments/open/create
Headers:
  Content-Type: application/json
  x-merchant-no: MCH_xxx
  x-app-key: tk_xxx
  x-app-secret: sk_xxx

Body:
{
  "amount": 9.90,
  "subject": "订单支付（可选，不填默认“订单支付”）",
  "merchantOrderNo": "商户订单号（可选，不传则系统自动生成）",
  "callbackUrl": "https://你的域名/a3/callback（可选）",
  "sourceRef": "场景名/备注（可选，用于你自己区分订单）"
}

{
  "success": true,
  "order": {
    "merchantOrderNo": "ORDER_20260614_0001",
    "status": "pending_payment",
    "payableAmountYuan": "9.90"
  },
  "payment": {
    "paymentId": "pay_xxx",
    "status": "created",
    "payUrl": "https://qr.alipay.com/xxxx"
  },
  "payPageUrl": "https://pay.a2569.com/gateway-pay?outNo=xxx"
}

/products   查看可下单商品
/buy        下单（默认商品）
/buyid 1053246   按商品ID下单
/status 订单号    查询订单状态
/statuspay 渠道单号 查询渠道状态
/resend 订单号    重新发送支付信息
/chat_id    查看当前会话/群ID
/merchant   查看当前绑定商户
/bindinfo   查看绑定信息（含商户号/接口地址等）

POST /api/payments/public/create
Body:
{
  "amount": 9.90,
  "subject": "订单支付",
  "merchantOrderNo": "ORDER_20260614_0001",
  "merchantNo": "MCH_xxx",
  "callbackUrl": "https://你的域名/a3/callback"
}

GET /api/payments/public/payment/{paymentId}?token={token}

GET /api/payments/public/merchant-qr-links/{merchantNo}
Query:
  amount=9.90   (可选；优先匹配固定金额二维码)

POST https://你的域名/a3/callback
Content-Type: application/json

{
  "success": true,
  "merchantOrderNo": "ORDER_20260614_0001",
  "paymentId": "pay_xxx",
  "orderId": "ord_xxx",
  "tradeStatus": "SUCCESS",
  "providerCode": "alipay_wap",
  "providerPaymentNo": "xxx",
  "transactionNo": "xxx"
}