30DaysOfTdd_Day14_Part9

        public Guid PlaceOrder(Guid customerId, ShoppingCart shoppingCart)
        {
            foreach (var item in shoppingCart.Items)
            {
                if (item.Quantity == 0)
                {
                    throw new InvalidOrderException();
                }
            }

            var order = new Order();
            return _orderDataService.Save(order);
        }