Add onDelete CASCADE to AbstractPageData.page_id FK

Without this, the fixture purger cannot delete Pages while AbstractPageData rows
still reference them via page_id (PostgreSQL RESTRICT default). CASCADE is the
correct semantic: a PageData without its template Page is meaningless and should
be removed with it.

Author: silverbackdan

src/Entity/Core/AbstractPageData.php

@@ -38,7 +38,7 @@
 abstract class AbstractPageData extends AbstractPage implements PageDataInterface
 {
     #[ORM\ManyToOne(targetEntity: Page::class)]
-    #[ORM\JoinColumn(name: 'page_id', nullable: false)]
+    #[ORM\JoinColumn(name: 'page_id', nullable: false, onDelete: 'CASCADE')]
     #[Assert\NotBlank(message: 'Please select a page template')]
     #[Groups(['Route:manifest:read'])]
     public Page $page;