var hashsalt = new HashAndSalt(passwordToRegister);

                                    var u = new User();
                                    u.email = emailToRegister;
                                    u.password = passwordToRegister;
                                    u.passwordHash = hashsalt.Hash;
                                    u.salt = hashsalt.Salt;
                                    u.username = emailToRegister;

                                    PostUser(u); // DODANIE UŻYTKOWNIKA

  public async void PostUser(User user)
        {
            await AddUser(user);
        }