constructor() {
    /**
     * @export {string|undefined}
     */
    this.access_token;

    /**
     * @export {string|undefined}
     */
    this.token_type;

    /**
     * @export {number|undefined}
     */
    this.expires_in;

    /**
     * @export {string|undefined}
     */
    this.error;
  }
The result of a token refresh. Passed by the token refresher to the callback
passed to it when it was called. 'expires_in' is in seconds.
@record @struct