IAV-24/feat(user): implement user management with controller, service, DTOs, and enhanced logging
- Added user management functionality with UserController and UserService implementation.
- Created UserController to handle user-related API endpoints for N8N instances, including retrieving, creating, deleting, and updating user roles.
- Implemented UserService interface and UserServiceImpl class to manage user operations, including API interactions and error handling.
- Added DTOs for user requests and responses: UserCreateRequestDTO, UserRoleUpdateRequestDTO, UserCreateResponseDTO, UserListResponseDTO, and UserResponseDTO.
- Enhanced logging for better traceability of user operations.