abstract class Repository  :2-5
  findById(String id) → T?  :3-3
  save(T entity) → Future<T>  :4-4
class UserService  :7-18
  getUser(String id) → User?  :12-12
  createUser(CreateUserDto data) → Future<User>  :14-14
class User  :20-24
hashPassword(String password) → String  :26-26
