public async void ItemClicked(object sender, EventArgs e)
        {
            try
            {
                var button = sender as Button;
                CheckoutPage.coupon = button.CommandParameter as Coupon;
                var response = await CartLogic.ApplyCoupon(Application.Current.Properties["user_id"].ToString(), CheckoutPage.coupon.id.ToString());

                if (response.status == 200)
                {
                    await Navigation.PopAsync();
                }
                else
                {
                    await DisplayAlert("Alert", response.message, "Ok");
                }
            }
            catch { }
        }