Users managing API end-points

[Avdhesh-Varshney]

1. Register User in our Database

`POST` http://localhost:5000/api/user/register
{
    "userId": "user_xxxxxxxxx",
    "firstName": "Abc",
    "lastName": "Xyz",
    "email": "abc@email.com",
    "imageUrl": "https://image.jpg"
}