Bundle attribute with compiler pass

Closes #3301682

core/lib/Drupal/Core/Entity/Attribute/Bundle.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\Entity\Attribute;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+
+/**
+ * Defines an attribute for registering a bundle class.
+ */
+#[\Attribute(\Attribute::TARGET_CLASS)]
+class Bundle {
+
+  /**
+   * Constructs a Bundle attribute object.
+   *
+   * @param string $entityTypeId
+   *   The entity type ID.
+   * @param string|null $bundle
+   *   The bundle ID, or NULL to use the entity type ID.
+   * @param \Drupal\Core\StringTranslation\TranslatableMarkup|null $label
+   *   The label of the bundle.
+   */
+  public function __construct(
+    // @todo see if we can infer the entity type automatically.
+    public string $entityTypeId,
+    public ?string $bundle = NULL,
+    public ?TranslatableMarkup $label = NULL,
+  ) {
+    $this->bundle ??= $this->entityTypeId;
+  }
+
+}