fix[litemall-db]: 订单号再次生成，需要添加日期

litemall-db/src/main/java/org/linlinjava/litemall/db/service/LitemallOrderService.java

@@ -64,7 +64,7 @@ public class LitemallOrderService {
         String now = df.format(LocalDate.now());
         String orderSn = now + getRandomNum(6);
         while (countByOrderSn(userId, orderSn) != 0) {
-            orderSn = getRandomNum(6);
+            orderSn = now + getRandomNum(6);
         }
         return orderSn;
     }