Changes

Implement service layer with comprehensive tests

- Added PersonService with CRUD operations
   - Added AdminService with business logic
   - Added UserService with validation
   - Created comprehensive unit tests for all services
   - Fixed exception handling declarations in tests

   Services include:
   - Create, read, update, delete operations
   - Input validation and error handling
   - Proper exception throwing for not found cases

   Tests include:
   - Happy path scenarios
   - Edge cases and error conditions
   - Proper exception testing
 (commit: 378d79b)