Add lesson 4

- Add initial `PostNodeRepository`
- Move logic to Repository
- Inject `EntityTypeManagerInterface`
- Add `PostNodeRepositoryTest`
- Add failing test method
- Failing test: non-existent service
- The "node" entity type does not exist.
- Create posts
- Add assertions based on the `created` date
- Sort nodes before returning them
- Return values to reset array keys

web/modules/custom/example/src/Repository/PostNodeRepository.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\example\Repository;
+
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\node\NodeInterface;
+
+final class PostNodeRepository {
+
+  public function __construct(
+    private EntityTypeManagerInterface $entityTypeManager,
+  ) {
+  }
+
+  /**
+   * @return array<int, NodeInterface>
+   */
+  public function findAll(): array {
+    $nodeStorage = $this->entityTypeManager->getStorage('node');
+    $nodes = $nodeStorage->loadMultiple();
+
+    uasort($nodes, function (NodeInterface $a, NodeInterface $b): int {
+      return $a->getCreatedTime() <=> $b->getCreatedTime();
+    });
+
+    return array_values($nodes);
+  }
+
+}