createSlice store a value returned from a promise function in redux-toolkit

I have a function consumed from a service where it returns a promise object when called, on fulfillment I need to extract a value.

 const isAdmin = some.service.isUserAuthorized({
        group: "group_id",
    }).then((response) => response.isAuthorized)
        .then((value) => {
            return value;
        });

const initialState = {user:"some_name",isAnAdmin:isAdmin }

// it provides promise object as the result, but i need the value of the promise object once completed

export const userDetailsSlice = createSlice({
  name: 'userDetails',
  initialState ,
  reducers: {
  },
})

export default userDetailsSlice.reducer