4d: Add the ArticleRepository

Create the `ArticleRepository` class and add it as a service.

This fails as there is no `getAll()` method on the class.

web/modules/custom/my_module/my_module.services.yml

@@ -0,0 +1,2 @@
+services:
+  Drupal\my_module\Repository\ArticleRepository: ~

web/modules/custom/my_module/src/Repository/ArticleRepository.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Drupal\my_module\Repository;
+
+class ArticleRepository {
+
+}
+

web/modules/custom/my_module/tests/src/Kernel/ArticleRepositoryTest.php

@@ -3,9 +3,14 @@
 namespace Drupal\Tests\my_module\Kernel;
 
 use Drupal\KernelTests\Core\Entity\EntityKernelTestBase;
+use Drupal\my_module\Repository\ArticleRepository;
 
 class ArticleRepositoryTest extends EntityKernelTestBase {
 
+  public static $modules = [
+    'my_module',
+  ];
+
   /** @test */
   public function nodes_that_are_not_articles_are_not_returned() {
     $repository = $this->container->get(ArticleRepository::class);