feat: implement idempotent soft delete for Books

[codesungrape]

This PR implements the "Soft Delete" functionality for the Book resource using a TDD approach. It ensures data is marked as deleted rather than physically removed, supporting audit requirements and data recovery.

Changes:

• BookService.java: Added deleteBookById method.
  • Logic is idempotent: Subsequent calls return success without triggering DB writes.
  • Added @transactional to ensure atomicity of the read/write operation.
• BookServiceTest.java: Added comprehensive unit tests covering:
  • Successful soft delete.
  • Resource not found (throws exception).
  • Idempotency (already deleted items do not trigger save).
• ResourceNotFoundException.java: Created custom exception to decouple business logic failures from framework exceptions.

Technical Decisions:

• Used Soft Delete (isDeleted flag) to preserve referential integrity.
• Implemented Strict Idempotency to ensure safe retries from the frontend.

[Copilot]

Pull Request Overview

This PR implements idempotent soft delete functionality for the Book resource following TDD principles. The implementation marks books as deleted rather than physically removing them, supporting audit requirements and data recovery needs.

Key Changes:

• Added deleteBookById method with idempotent behavior ensuring repeated deletions don't trigger unnecessary database writes
• Comprehensive test coverage including success, not found, and idempotency scenarios
• Custom ResourceNotFoundException to handle business logic failures distinct from framework exceptions

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/main/java/com/codesungrape/hmcts/bookapi/service/BookService.java	Implements soft delete with @Transactional annotation and idempotent logic
src/test/java/com/codesungrape/hmcts/bookapi/BookServiceTest.java	Adds unit tests covering successful deletion, not found exception, and idempotency
src/main/java/com/codesungrape/hmcts/bookapi/exception/ResourceNotFoundException.java	New custom runtime exception for resource not found scenarios
build.gradle	Enhances JaCoCo report output with file path printing
README.md	Updates JaCoCo report file path to reflect actual location

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