trait MoreInfoTrait in Markdown 8.2

trait MoreInfoTrait {
  use RendererTrait;

  /**
   * Appends existing content with a "More Info" link.
   *
   * @param mixed $existing
   *   The existing content to append to.
   * @param string|\Drupal\Core\Url $url
   *   The URL to use.
   * @param string $label
   *   Optional. The "More Info" label to use for the link.
   *
   * @return \Drupal\Component\Render\MarkupInterface
   *   The new joined content.
   */
  protected function moreInfo($existing, $url, $label = 'More Info') {
    if (!$url) {
      return $existing;
    }
    if (!$url instanceof Url) {
      $url = UrlHelper::isExternal($url) ? Url::fromUri($url)
        ->setOption('attributes', [
        'target' => '_blank',
      ]) : Url::fromUserInput($url);
    }
    if (!$label instanceof MarkupInterface) {
      $label = $this
        ->t($label);

      // phpcs:ignore
    }
    $build = [
      '#type' => 'link',
      '#title' => new FormattableMarkup('[@label]', [
        '@label' => $label,
      ]),
      '#url' => $url,
      '#options' => [
        'attributes' => [
          'class' => [
            'installable-more-info',
          ],
          'title' => $label,
        ],
      ],
      '#prefix' => ' ',
    ];
    $moreInfo = $this
      ->renderer()
      ->renderPlain($build);
    if (empty($existing) || empty(trim($existing))) {
      return $moreInfo;
    }
    return new FormattableMarkup('@existing @moreInfo', [
      '@existing' => $existing,
      '@moreInfo' => $moreInfo,
    ]);
  }

}