feat: add Airwallex payments and multi-currency support

backend/internal/handler/payment_webhook_handler.go

@@ -2,6 +2,7 @@ package handler
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -60,6 +61,12 @@ func (h *PaymentWebhookHandler) StripeWebhook(c *gin.Context) {
 	h.handleNotify(c, payment.TypeStripe)
 }
 
+// AirwallexWebhook 处理空中云汇 Webhook 事件。
+// POST /api/v1/payment/webhook/airwallex
+func (h *PaymentWebhookHandler) AirwallexWebhook(c *gin.Context) {
+	h.handleNotify(c, payment.TypeAirwallex)
+}
+
 // handleNotify is the shared logic for all provider webhook handlers.
 func (h *PaymentWebhookHandler) handleNotify(c *gin.Context, providerKey string) {
 	var rawBody string
@@ -146,6 +153,17 @@ func extractOutTradeNo(rawBody, providerKey string) string {
 		if err == nil {
 			return values.Get("out_trade_no")
 		}
+	case payment.TypeAirwallex:
+		var payload struct {
+			Data struct {
+				Object struct {
+					MerchantOrderID string `json:"merchant_order_id"`
+				} `json:"object"`
+			} `json:"data"`
+		}
+		if err := json.Unmarshal([]byte(rawBody), &payload); err == nil {
+			return strings.TrimSpace(payload.Data.Object.MerchantOrderID)
+		}
 	}
 	// For other providers (Stripe, Alipay direct, WxPay direct), the registry
 	// typically has only one instance, so no instance lookup is needed.
@@ -183,14 +201,14 @@ const (
 	wxpaySuccessMessage = "成功"
 )
 
-// writeSuccessResponse sends the provider-specific success response.
-// WeChat Pay requires JSON {"code":"SUCCESS","message":"成功"};
-// Stripe expects an empty 200; others accept plain text "success".
+// writeSuccessResponse 返回各支付服务商要求的成功响应。
+// 微信支付需要 JSON {"code":"SUCCESS","message":"成功"}；
+// Stripe 和空中云汇接受空 200，其它服务商接受纯文本 "success"。
 func writeSuccessResponse(c *gin.Context, providerKey string) {
 	switch providerKey {
 	case payment.TypeWxpay:
 		c.JSON(http.StatusOK, wxpaySuccessResponse{Code: wxpaySuccessCode, Message: wxpaySuccessMessage})
-	case payment.TypeStripe:
+	case payment.TypeStripe, payment.TypeAirwallex:
 		c.String(http.StatusOK, "")
 	default:
 		c.String(http.StatusOK, "success")