Motivation

• Ensure countByLibraryId reports the number of books in a library that actually have book files (and are not deleted), aligning it with the behavior of other book-type counting queries.

Description

• Replace the previous simple count JPQL for countByLibraryId with a query that JOINs b.bookFiles bf, filters on bf.isBookFormat = true, and uses COUNT(DISTINCT b) to only count books that have book files and are not deleted.
• Add countByLibraryId_countsOnlyBooksWithBookFiles to BookRepositoryDataJpaTest which persists a library, a file-backed book, a fileless book, and a deleted file-backed book, then asserts that bookRepository.countByLibraryId(...) returns 1.

Testing

• Ran the repository data JPA tests (BookRepositoryDataJpaTest) which include the new countByLibraryId_countsOnlyBooksWithBookFiles test, and they passed.

Codex Task