Add missing unit tests for UserService and AuthService

[vizahat36]

Related to #109

This PR adds missing unit tests for the User Management service layer.

What was added:

• UserServiceTest: covers registration, username checks, user listing, and password change logic
• AuthServiceTest: covers authentication/login success and failure cases

Notes:

• Controller tests already existed and were not modified
• Tests are written with JUnit 5 and Mockito
• All tests are fast, isolated, and do not depend on DB or network

Test verification:

• ./mvnw test passes successfully (27 tests, 0 failures)

[Copilot]

Pull request overview

This PR adds comprehensive unit tests for the UserService and AuthService classes to improve test coverage of the service layer. The tests use JUnit 5 and Mockito for isolated, fast testing without external dependencies.

Changes:

• Added UserServiceTest with 7 test cases covering user registration, username validation, user listing, and password changes
• Added AuthServiceTest with 3 test cases covering login success and failure scenarios
• All tests follow existing project patterns and use proper mocking with MockitoExtension

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
backend/src/test/java/vaultWeb/services/auth/AuthServiceTest.java	Adds unit tests for AuthService login functionality with success and failure cases
backend/src/test/java/vaultWeb/services/UserServiceTest.java	Adds comprehensive unit tests for UserService covering registration, username checks, user listing, and password management

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[vizahat36]

@DenizAltunkapan whenever you have time, could you please take a look at this PR? Thank you.

For clarity: user roles in the current codebase are applied at the group/member domain level and not within the UserService or AuthService logic. This PR focuses on unit testing the user lifecycle and authentication flow, which aligns with the scope of Issue #109.

[DenizAltunkapan]

@vizahat36 please format your code using spotless

[vizahat36]

@DenizAltunkapan
Thanks for the heads-up! I’ve applied Spotless formatting and pushed an update. Please let me know if anything else is needed.

[DenizAltunkapan]

@vizahat36 Thank you for your contribution. I changed the keyword from “fixes” to “related to” so the issue stays open and others can open follow-up PRs for testing purposes.