lindaquinoa/lesson_23/Implemented MediaItemsController with complete CRUD operations

[lquinoa252]

• GET /items - Retrieve all media items (returns 200 with array)
• GET /items/{id} - Retrieve specific media item by ID (returns 200 or 404)
• POST /items - Create new media item (returns 200 with created item)
• DELETE /items/{id} - Remove media item by ID (returns 204 or 404)

Implementation Details:

• No try/catch blocks, let Spring handle validation
• Used TypeScript pattern as reference for clean controller structure
• Class-level @RequestMapping("/api/v1/media") annotation
• Proper HTTP status codes and error handling
• All endpoints use Librarian authorization for library operations

Testing:

• All 7 unit tests passing
• Manual API testing with curl verified all endpoints working correctly
• Changes isolated to single file: MediaItemsController.java