添加新的支付方式：Stripe

src/main/java/com/ai/da/service/StripeService.java

@@ -5,7 +5,11 @@ import javax.servlet.http.HttpServletResponse;
 
 public interface StripeService {
 
-    String pay(Integer quantity);
+    String pay(Integer quantity, String returnUrl);
 
     Boolean notify(HttpServletRequest request);
+
+    String refund(String amount, String orderId, String reason);
+
+    void checkOrderStatus(String orderNo);
 }