Implementing a custom LinkHandler

<?php
namespace T3docs\Examples\LinkHandler;

# use ...
use TYPO3\CMS\Recordlist\LinkHandler\LinkHandlerInterface;

class GitHubLinkHandler implements LinkHandlerInterface
{
   protected $linkAttributes = ['target', 'title', 'class', 'params', 'rel'];
   protected $view;
   protected $configuration;

   /**
   * Initialize the handler
   *
   * @param AbstractLinkBrowserController $linkBrowser
   * @param string $identifier
   * @param array $configuration Page TSconfig
   */
   public function initialize(AbstractLinkBrowserController $linkBrowser, $identifier, array $configuration)
   {
      $this->linkBrowser = $linkBrowser;
      $this->iconFactory = GeneralUtility::makeInstance(IconFactory::class);
      $this->view = GeneralUtility::makeInstance(StandaloneView::class);
      $this->view->getRequest()->setControllerExtensionName('examples');
      $this->view->setTemplateRootPaths([GeneralUtility::getFileAbsFileName('EXT:examples/Resources/Private/Templates/LinkBrowser')]);
      $this->configuration = $configuration;
   }

   /**
   * Checks if this is the handler for the given link
   *
   * Also stores information locally about currently linked issue
   *
   * @param array $linkParts Link parts as returned from TypoLinkCodecService
   *
   * @return bool
   */
   public function canHandleLink(array $linkParts)
   {
      if (isset($linkParts['url']['github'])) {
         $this->linkParts = $linkParts;
         return true;
      }
      return false;
   }

   /**
   * Format the current link for HTML output
   *
   * @return string
   */
   public function formatCurrentUrl(): string
   {
      return $this->linkParts['url']['github'];
   }


   /**
   * Render the link handler
   *
   * @param ServerRequestInterface $request
   *
   * @return string
   */
   public function render(ServerRequestInterface $request): string
   {
      GeneralUtility::makeInstance(PageRenderer::class)
         ->loadRequireJsModule('TYPO3/CMS/Examples/GitHubLinkHandler');

      $this->view->assign('project', $this->configuration['project']);
      $this->view->assign('action', $this->configuration['action']);
      $this->view->assign('github', !empty($this->linkParts) ? $this->linkParts['url']['github'] : '');
      return $this->view->render('GitHub');
   }

   /**
   * @return string[] Array of body-tag attributes
   */
   public function getBodyTagAttributes(): array
   {
      return [];
   }

   /**
   * @return array
   */
   public function getLinkAttributes()
   {
      return $this->linkAttributes;
   }

   /**
   * @param string[] $fieldDefinitions Array of link attribute field definitions
   * @return string[]
   */
   public function modifyLinkAttributes(array $fieldDefinitions)
   {
      return $fieldDefinitions;
   }

   /**
   * We don't support updates since there is no difference to simply set the link again.
   *
   * @return bool
   */
   public function isUpdateSupported()
   {
      return FALSE;
   }
}

TCEMAIN.linkHandler {
   github {
      handler = T3docs\\Examples\\LinkHandler\\GitHubLinkHandler
      label = LLL:EXT:examples/Resources/Private/Language/locallang_browse_links.xlf:github
      displayAfter = url
      scanBefore = url
      configuration {
          project = TYPO3-Documentation/TYPO3CMS-Reference-CoreApi
          action = issues
      }
   }
}

/**
 * Module: TYPO3/CMS/Examples/GitHubLinkHandler
 * Github issue link interaction
 */
define(['jquery', 'TYPO3/CMS/Recordlist/LinkBrowser'], function($, LinkBrowser) {
   'use strict';

   /**
    *
    * @type {{}}
    * @exports T3docs/Examples/GitHubLinkHandler
    */
   var GitHubLinkHandler = {};

   $(function() {
      $('#lgithubform').on('submit', function(event) {
         event.preventDefault();

         var value = $(this).find('[name="lgithub"]').val();
         if (value === 'github:') {
            return;
         }
         if (value.indexOf('github:') === 0) {
            value = value.substr(7);
         }
         LinkBrowser.finalizeFunction('github:' + value);
      });
   });

   return GitHubLinkHandler;
});

<a href="github:123">Example Link</a>