Jak przeprowadzic uwierzytelnianie za pomoca useMutation ?

Robie rejestrowanie uzytkownika za pomoca useMutation, server otrzymuje request , wsadza nowego uzytkownika do bazy i wysyla jego dane do mutatora, ale alert
w useRegister pokazuje data:{}
jak to poprawic ?

 const mutator = useRegister();
  const register = async (data: User) => {
    mutator.mutate(data);
    alert("mutate" + JSON.stringify(mutator));                                            //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>  ten komunikat    
  };

import { Register } from "../../../utils/auth";
const useRegister = () => {
  const queryClient = useQueryClient();
  const mutator = useMutation(async (user: User) => {
    return (
      await Register("register", user),
      {
        onSettled: async () => {
          alert("ssss  " + JSON.stringify(mutator));
        },
      }
    );
  });
  return mutator;
};
export { useRegister };

const Register = async (url: string, data: User) => {
  return (
    await api.post<User>(BASE_URL + url, data),
    {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify(data),
    }
  );
};
export { Register }

import axios from "axios";
export const api = {
  get: <T>(url: string, params?: object) =>
    axios.get<T>(url, {
      ...params,
    }),
  post: <T>(url: string, data: any) => axios.post<T>(url, data, {}),
  patch: <T>(url: string, data: any) => axios.patch<T>(url, data, {}),
  delete: <T>(url: string) => axios.delete<T>(url, {}),
};

funkcja realizujace rzadanie na serwerze wyglada tak

export const register = async (req, res) => {
  try {
    const {
      firstName,
      lastName,
      email,
      password,
      picturePath,
      friends,
      location,
      occupation,
    } = req.body;
    console.log("eeeeeeeeeeeeeeeeeeeeeeeeeeeeee");

    const salt = await bcrypt.genSalt();
    const passwordHash = await bcrypt.hash(password, salt);
    if (
      usersarr.filter((t) => {
        return t.email === email || (t.password === password && t);
      }).length > 0
    ) {
      res.status(404).json({ message: "already exists user" });
      console.log(1111111);
    } else {
      usersarr.push({
        _id: new Date().getTime(),
        firstName,
        lastName: "sssssss",
        email: email,
        password: passwordHash,
        picturePath,
        friends: [],
        location: "New York",
        occupation: "private",
        viewedProfile: Math.floor(Math.random() * 10000),
        impressions: Math.floor(Math.random() * 10000),
      });

      res.status(201).json(
        usersarr.filter((t) => {
          return t.email === email && t;
        })[0]
      );
      console.log(
        usersarr.filter((t) => {
          return t.email === email && t;
        })[0]
      );
    }
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
};

Nie da się przeprowadzić autentykacji ponieważ takie słowo nie istnieje.