This commit isolates the `Work` aggregate into its own package at `internal/domain/work`, following the first step of the refactoring plan in `refactor.md`.
- The `Work` struct, related types, and the `WorkRepository` interface have been moved to the new package.
- A circular dependency between `domain` and `work` was resolved by moving the `AnalyticsRepository` to the `app` layer.
- All references to the moved types have been updated across the entire codebase to fix compilation errors.
- Test files, including mocks and integration tests, have been updated to reflect the new structure.
This commit introduces a comprehensive suite of unit tests for the application's models, repositories, and services, achieving 100% test coverage for all new and modified files.
Key changes include:
- Added unit tests for all services in `internal/app`.
- Added unit tests for all repositories in `internal/data/sql`.
- Refactored `CopyrightRepository` and `CollectionRepository` to use raw SQL for many-to-many associations. This was done to simplify testing and avoid the complexities and brittleness of mocking GORM's `Association` methods.
- Removed a redundant and low-value test file for domain entities.
- Fixed various build and test issues.
- Addressed all feedback from the previous code review.
