public ActionResult AddPayment(AddPaymentViewModel newPayment)
 {
     using (var rdbc = new RavenDbConnection(_rdcm))
     {
         var orderService = new OrderService(rdbc);
         orderService.AddPayment(newPayment.OrderId, newPayment.PaymentId, newPayment.PaymentAmount);
     }
     return RedirectToAction("Index", "Orders");
 }