title: add custom header to all laravel socialite requests
body: <p>I'm using socialite with a custom provider that requires an <code>X-User-Agent</code> header for all requests to the API. I've tried using this format in my <code>routes/web.php</code> but the API still throws an error that the header is not found:</p>
  <pre><code>$user = Socialite::driver('myprovider')
      -&gt;with(['X-User-Agent' =&gt; 'CustomValue'])
      -&gt;user();
  </code></pre>
  <p>Is there a place I can add this custom header to all requests to the provider?</p>