Fix issue #4: Book API source model

[cld-vasconcelos]

This pull request fixes #4.

The issue has been successfully resolved. The agent has created a comprehensive model for storing different book API sources in the database with all necessary components:

1. Created a BookApiSource interface in types/book.ts with fields for id, name, code, baseUrl, apiKey, isActive, and timestamps.

2. Added a database migration file (20250402000000_add_book_api_sources.sql) that:

   • Creates a book_api_sources table with appropriate columns
   • Sets up row-level security policies
   • Adds default sources (Google Books API, Open Library API, Libro Database)
   • Modifies the existing user_books table to reference the new source codes

3. Implemented a complete service (bookApiSourceService.ts) with CRUD operations:

   • getBookApiSources() - fetches all sources
   • getBookApiSourceByCode() - fetches a specific source by code
   • createBookApiSource() - creates a new source
   • updateBookApiSource() - updates an existing source
   • deleteBookApiSource() - deletes a source

4. Added comprehensive unit tests for all service functions in bookApiSourceService.test.ts

The implementation is thorough and addresses all aspects of the issue, providing a complete solution for storing and managing different book API sources in the database.

Automatic fix generated by OpenHands 🙌