public void AddUser(string login, string password)
        {
            if (string.IsNullOrWhiteSpace(password))
            {
                throw new InvalidParamsError();
            }

            if (_repository.LoginAlreadyTaken(login))
            {
                throw new LoginTakenError();
            }

            byte[] passwordHash, passwordSalt;
            PasswordManager.CreatePasswordHash(password, out passwordHash, out passwordSalt);

            User user = new User()
            {
                Login        = login,
                Guid         = Guid.NewGuid().ToString(),
                PasswordHash = passwordHash,
                PasswordSalt = passwordSalt,
            };

            _repository.AddUser(user);
        }