public void MoveBetweenAccount()
        {
            using (var client = CreateClient())
            {
                var accountRef = new AccountRef
                                 {
                                     AppAccountId = UserId
                                 };
                var payment = new Payment
                              {
                                  Amount = AMOUNT,
                                  Beneficiary = accountRef,
                                  Message = "Test -" + TimedId
                              };
                var result = client.PostPayment(payment, CHARGED_USER_ID);
                Assert.IsNotNull(result);
                Assert.AreEqual(CHARGED_USER_ID, result.Sender.AppAccountId);

                accountRef.AppAccountId = CHARGED_USER_ID;

                result = client.PostPayment(payment, UserId);
                Assert.IsNotNull(result);
                Assert.AreEqual(UserId, result.Sender.AppAccountId);
            }
        }
        // Not implemented
        //public int GetPaymentsCount(string userId = null)
        //{
        //    var uri = CreateUri(userId, payments);
        //    return GetCount(uri);
        //}

        public Payment PostPayment(Payment payment, string userId = null)
        {
            var uri = CreateUri(userId, payments);
            return PostAsync(uri, payment);
        }