Store the Auth0 user id in a protected endpoint

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1

In the example auth0 provides for Storing an Auth0 user id in a remote system it posts to an unprotected endpoint. Are there headers or something I can add to the request that my endpoint can check to make sure not just anyone can post a email and create a user?

const axios = require("axios");

/**
 * @param {Event} event - Details about registration event.
 */
exports.onExecutePostUserRegistration = async (event) => {
  await axios.post("https://my-api.exampleco.com/users", { params: { email: event.user.email }});
};