Fix type of output property in ChannelPostRender

Closes #3387056

src/Event/ChannelPostRender.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\push_framework\Event;
 
+use Drupal\Component\Render\MarkupInterface;
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\push_framework\ChannelPluginInterface;
 use Drupal\user\UserInterface;
@@ -14,14 +15,14 @@ class ChannelPostRender extends ChannelEventLanguageBase {
   /**
    * The rendered notification message.
    *
-   * @var string
+   * @var string|\Drupal\Component\Render\MarkupInterface
    */
-  protected string $output;
+  protected string|MarkupInterface $output;
 
   /**
    * {@inheritdoc}
    */
-  public function __construct(ChannelPluginInterface $channelPlugin, UserInterface $user, ContentEntityInterface $entity, string $displayMode, string $languageKey, string &$output) {
+  public function __construct(ChannelPluginInterface $channelPlugin, UserInterface $user, ContentEntityInterface $entity, string $displayMode, string $languageKey, string|MarkupInterface &$output) {
     parent::__construct($channelPlugin, $user, $entity, $displayMode, $languageKey);
     $this->output = &$output;
   }
@@ -29,23 +30,23 @@ class ChannelPostRender extends ChannelEventLanguageBase {
   /**
    * Get the rendered notification message.
    *
-   * @return string
+   * @return string|\Drupal\Component\Render\MarkupInterface
    *   The rendered notification message.
    */
-  public function getOutput(): string {
+  public function getOutput(): string|MarkupInterface {
     return $this->output;
   }
 
   /**
    * Set the rendered notification message.
    *
-   * @param string $output
+   * @param string|\Drupal\Component\Render\MarkupInterface $output
    *   The rendered notification message.
    *
    * @return ChannelPostRender
    *   This.
    */
-  public function setOutput(string $output): ChannelPostRender {
+  public function setOutput(string|MarkupInterface $output): ChannelPostRender {
     $this->output = $output;
     return $this;
   }