public static string UpdateCartController(Cart cart, int productId)
        {
            int equal = AddToCartHandler.returnStock(productId);

            if (cart.Quantity < 0)
            {
                return("Input Invalid!");
            }
            else if (equal < cart.Quantity)
            {
                return("There's not enough stock for that product");
            }
            CartHandler.UpdateCartHandler(cart);
            return("Success");
        }