Draft: Test feature

Summary by Bito

This pull request implements a Book Store Management System with model classes, service interfaces, and implementations for Book and User management. It includes database utilities, custom exceptions, and a ResponseCode enum for standardized HTTP responses. A new StoreUtil class has been added for common store operations.

Code change type: Feature Addition, Structuring, Configuration Changes

Unit tests added: False

Estimated effort to review (1-5, lower is better): 4