Modify _all_ Drupal links

LinkModifierService.php

<?php

namespace Drupal\wt_base;
use Symfony\Component\HttpFoundation\RequestStack;
use Drupal\Core\PathProcessor\OutboundPathProcessorInterface;
use Symfony\Component\HttpFoundation\Request;
use Drupal\Core\Render\BubbleableMetadata;

/**
 * Class DefaultService.
 */
class LinkModifierService implements OutboundPathProcessorInterface {

  /**
   * Symfony\Component\HttpFoundation\RequestStack definition.
   *
   * @var \Symfony\Component\HttpFoundation\RequestStack
   */
  protected $requestStack;
  /**
   * Constructs a new DefaultService object.
   */
  public function __construct(RequestStack $request_stack) {
    $this->requestStack = $request_stack;
  }

  /**
   * {@inheritdoc}
   */
  public function processOutbound($path, &$options = array(), Request $request = NULL, BubbleableMetadata $bubbleable_metadata = NULL) {

    if (empty($request)) {
      $request = $this->requestStack->getCurrentRequest();
    }
    // On every page of type "product" add the product id as query parameter to every link on that page
    // no matter if that link is in a menu, a block or in a CKeditor text field of the node.
    // It does only modify interal though, but not links to external homepages.
    $node = $request->attributes->get('node');
    if ($node && $node->bundle() === 'product') {
      $options['query'][] = [$node->bundle() => $node->id()];
    }

    return $path;
  }  

}

wt_base.services.yml

services:
  wt_base.link_modifier_service:
    class: Drupal\wt_base\LinkModifierService
    tags:
      - { name: path_processor_outbound, priority: 3000 }
    arguments: ['@request_stack']