how to update intercom user and clear the user_id value

index.js

// currently this does not work, we get 2xx return code but user_id is still on record

const axios = require("axios");
var basicAuth = {
  auth: {
    username: process.env.INTERCOM_TOKEN,
    password: "",
  },
};
var id = 'intercom user id';
var data = { external_id: '' };
await axios.put("https://api.intercom.io/contacts/" + id, data, basicAuth);