Added endpoints to manage collaborators in `ProjectsController`:
- Add collaborator
- Remove collaborator
- Get project collaborators
Updated `ProjectsService` with corresponding methods and enhanced `checkUserAccess` to validate user access as owner or collaborator. Included unit tests for new functionality in controllers and services.
Added comprehensive unit tests for `PersonsController`, `PersonsService`, `ProjectsController`, and `ProjectsService`. Covered CRUD operations, exception handling, group/project associations, and user access validation. Mocked `JwtAuthGuard` for all tests.
