public void ProcessRequest(HttpContext context)
        {
            var service = new HostedService(new ServicesConfig
            {
                MerchantId          = "heartlandgpsandbox",
                AccountId           = "hpp",
                SharedSecret        = "secret",
                ServiceUrl          = "https://pay.sandbox.realexpayments.com/pay",
                HostedPaymentConfig = new HostedPaymentConfig
                {
                    Language = "en",
                },
            });

            var json = service.Authorize(100)
                       .WithCurrency("EUR")
                       .Serialize();

            context.Response.ContentType = "application/json";
            context.Response.Write(json);
        }