AUDIT-14: Add unit tests for mapAuditEntitiesToDetails

[yousung1020]

Description of what I changed

• added a comprehensive unit test for mapAuditEntitiesToDetails in AuditServiceImpl.
• implemented shouldMapAuditEntitiesToDetails_WithChangedFields to verify the transformation of AuditEntity into AuditLogDetailDTO.
• utilized MockedStatic to isolate the unit test from the OpenMRS runtime environment, specifically for UserService and resolveUsername logic.
• leveraged the existing TestEntity class to simulate entity revisions and ensure that metadata (Revision ID, Changed By) is correctly mapped.
• verified that the service correctly interacts with AuditDao to fetch the previous revision for comparison.

Issue I worked on

see https://openmrs.atlassian.net/browse/AUDIT-14

Checklist: I completed these to help reviewers :)

• My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master