Nightwatch.js - sending custom HTTP request headers

Question

I searched for an answer about this, but could not find it. I use nightwatch.js to write UI tests. It works fine, but I need to send custom headers for HTTP requests, as the application is protected by digital signage and does not have a login form that tests can use to access the site itself.

I am looking for something similar that can be installed in PhantomJS, but for my nightwatch.json configuration or the tests themselves.

Is it possible?

    var webPage = require('webpage');
    var page = webPage.create();

    page.customHeaders = {
      "X-Test": "foo",
      "DNT": "1"
    };

    page.onInitialized = function() {
      page.customHeaders = {};
    };