title: Where to set Jenkins root URL in the GUI?
body: <p>Jenkins is giving me a warning:</p>
  
  <blockquote>
    <p>Jenkins root URL is empty but is required for the proper operation of
    many Jenkins features like email notifications, PR status update, and
    environment variables such as BUILD_URL. Please provide an accurate
    value in Jenkins configuration.</p>
  </blockquote>
  
  <p>The link to Jenkins configuration is /configure, but there is no "Root URL" field there. Where can this be set?</p>