Implement Registration backend service API

[oguzhanural]

As a backend developer I need to Implement Registration backend service API So that users can create new accounts on the platform.

Details and Assumptions

* The API should support user registration by collecting necessary details such as username, email and password.
* The API should validate input data for correctness and uniqueness (e.g., unique email).
* The API should securely store user credentials using encryption.
* The API should send a confirmation email to the user upon successfully registration.
* Proper error handling and responses should be implemented.

Acceptance Criteria

gherkin
Given the requirements for the Registration backend service API
When I implement the API
Then the API should accept user details for registration
And the API should validate and store user information securely
And the API should send a confirmation email to the user
And the API should provide proper error handling and responses

[oguzhanural]

I'm working on it.