Checks the status of a payment.
**Response: SUCCESS (200 OK)**
{
"code": 200,
"status": success,
"custom": 123456789ABCD,
"merchant_email": merchant@gmail.com,
"username":"john",
"email": user@email.com,
}
Expected statuses are 'INITIATED', 'SUCCESS', 'PENDING', 'HOLD'.