refactor(http): rename statusCode to status_code and prevent email exposure in response

[AdeGneus]

Pull Request: Improve HTTP Response Format & Enhance Security in Newsletter Unsubscribe

Description

This PR introduces the following improvements:

• Refactored error responses: Changed statusCode to status_code for consistency.
• Enhanced security in error messages: Updated NotFoundException response to avoid exposing user emails.
• Applied changes globally through the HttpExceptionFilter.

Related Issue

Fixes #(issue)

Type of Change

• feat: New feature
• fix: Bug fix
• docs: Documentation updates
• style: Code style/formatting changes
• refactor: Code refactoring
• perf: Performance improvements
• test: Test additions/updates
• chore: Build process or tooling changes
• ci: CI configuration changes
• other:

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual tests

Test Evidence

Tested Changes:

• Verified that all error responses now use status_code instead of statusCode.
• Confirmed NotFoundException no longer reveals user email.
• Unit tests updated and passing successfully.

Screenshots (if applicable)

before:

after:

Documentation Screenshots (if applicable)

Checklist

• My code follows the project's coding style
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published
• I have included a screenshot showing all tests passing
• I have included documentation screenshots (if applicable)

Additional Notes

• These changes improve API consistency and enhance security.
• No breaking changes introduced.