[Feature]: Refactor Auth Controller for Code Reuse & Readability

[akofficial10]

Description:
The register and login controllers currently work fine, but they contain repeated logic such as:

1. Input normalization (trimming and lowercasing strings).
2. Building the user response object.
3. Handling repeated validation patterns.

This repetition makes the code harder to maintain and more error-prone when future changes are needed (e.g., updating the response structure).

Expected improvement:

1. Reduce duplication in the auth controller.
2. Improve readability and maintainability.
3. Keep functionality, validation, and API responses exactly the same.

[github-actions]

Thank you for raising this issue!

We'll review it as soon as possible. We truly appreciate your contributions! ✨

Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊

[GollaBharath]

Since you already have a issue assigned to you, i will wait for someone else to take this up. Or you can submit a PR for the previous issue and then ask me to assign this to you.

[akofficial10]

@GollaBharath but there are only 2 issues not many so you can assign both.

[GollaBharath]

Yes but I want to give others a chance too, So currently only 1 issue per person at a given time.