Add a Presentation bundle class

Drupal core issue: https://www.drupal.org/node/2570593
Change record: https://www.drupal.org/node/3191609

modules/opd_presentations/src/Entity/Presentation.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\opd_presentations\Entity;
+
+use Drupal\node\Entity\Node;
+use Drupal\node\NodeInterface;
+
+final class Presentation extends Node implements NodeInterface {
+
+  public function getPastEvents(): array {
+    return $this->get('field_events')->referencedEntities();
+  }
+
+}