Implement validate registration with pin

[stephane-segning]

• User Story: User story-11: As a potential user using choronko will like to register with the PowerPay system #7
• Description: A user would receive a OTP and send it with his pin, so that we should hash it and save it in the database. It'll use the SMS API Gateway for communicating with our P.P. Service.
• Blocker: Implement the Logic for Creating a User in the backend #12