public void SubmitOrder(OrderData data)
        {
            // call the domain model for regular order submit logic
            var customer = GetCustomer(data.CustomerId);
            var shoppingCart = GetShoppingCart(data.CartId);

            // if (customer.UnpaidOrdersAmount + shoppingCart.Total > Max)
            // {
            // 	// fail (no discussion of exceptions vs returns codes here)
            // }
            // else
            // {
            // 	customer.Purchase(shoppingCart);
            // }

            customer.Purchase(shoppingCart);
        }