This commit addresses all the high-priority tasks outlined in the TASKS.md file, significantly improving the application's observability, completing key features, and refactoring critical parts of the codebase.
### Observability
- **Centralized Logging:** Implemented a new structured, context-aware logging system using `zerolog`. A new logging middleware injects request-specific information (request ID, user ID, trace ID) into the logger, and all application logging has been refactored to use this new system.
- **Prometheus Metrics:** Added Prometheus metrics for database query performance by creating a GORM plugin that automatically records query latency and totals.
- **OpenTelemetry Tracing:** Fully instrumented all application services in `internal/app` and data repositories in `internal/data/sql` with OpenTelemetry tracing, providing deep visibility into application performance.
### Features
- **Analytics:** Implemented like, comment, and bookmark counting. The respective command handlers now call the analytics service to increment counters when these actions are performed.
- **Enrichment Tool:** Built a new, extensible `enrich` command-line tool to fetch data from external sources. The initial implementation enriches author data using the Open Library API.
### Refactoring & Fixes
- **Decoupled Testing:** Refactored the testing utilities in `internal/testutil` to be database-agnostic, promoting the use of mock-based unit tests and improving test speed and reliability.
- **Build Fixes:** Resolved numerous build errors, including a critical import cycle between the logging, observability, and authentication packages.
- **Search Service:** Fixed the search service integration by implementing the `GetWorkContent` method in the localization service, allowing the search indexer to correctly fetch and index work content.
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.
