增加预订单回调处理，用于扩展信息

pay-java-union/src/main/java/com/egzosn/pay/union/api/UnionPayService.java

@@ -288,7 +288,7 @@ public class UnionPayService extends BasePayService<UnionPayConfigStorage> {
                 params.put(SDKConstants.param_payTimeout, getPayTimeout(order.getExpirationTime()));
                 params.put("orderDesc", order.getSubject());
         }
-
+        params =  preOrderHandler(params, order);
         return setSign(params);
     }