Issue #2570593: Allow entities to be subclassed using "bundle classes"

Rebased for 9.3.x.

core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php

@@ -214,7 +214,8 @@ protected function doLoadMultiple(array $ids = NULL) {
   protected function doCreate(array $values) {
     // Set default language to current language if not provided.
     $values += [$this->langcodeKey => $this->languageManager->getCurrentLanguage()->getId()];
-    $entity = new $this->entityClass($values, $this->entityTypeId);
+    $entity_class = $this->getEntityClass();
+    $entity = new $entity_class($values, $this->entityTypeId);
 
     return $entity;
   }