限购商品购买前验证接口添加错误信息字段

Code Review By Rock Zhang

@@ -345,6 +345,7 @@ class CartModel
             if (!$pay || $pay['code'] != 200 || empty($pay['data']['goods_list'])) {
                 if ($isLimitGoods) {
                     $result['error'] = true;
+                    $result['message'] = $pay['message'];
                 } else {
                     $result['cartUrl'] = Helpers::url('/cart/index/index');
                 }