Redirect to www.drupal.org when a node is found, but type is not yet allowed

For /browse/recipes, the nodes should still be viewed on www.drupal.org since they are not ready to really move over yet. I haven’t done anything special in the View to link to the legacy site. Instead, this change redirects to the same node on www.drupal.org when the content type is not ready. This way when there's any relative link in migrated content, there’s some capability to route to the right site without updating the content; and we're not hard-coding the sites into Views or elsewhere.

This also removes the bypass node access ability. I think for production, less differences in what admins can see vs. other user accounts is always good. We could open up a "preview" phase where a separate allowlist of content types is viewable by admins with bypass node access. I'm guessing the bypass node access exception might have been added so we can preview how something like credit records are migrating.

src/EventSubscriber/AllowedContentTypes.php

@@ -87,12 +87,19 @@ class AllowedContentTypes implements EventSubscriberInterface {
       $node = $this->currentRouteMatch->getParameter('node');
       if ($node) {
         /** @var \Drupal\node\Entity\Node $node */
-        if (!in_array($node->bundle(), $allowed_types) && !$this->currentUser->hasPermission('bypass node access')) {
-          $this->messenger->addWarning(t('It is not allowed to edit %type pages in the site yet.', [
-            '%type' => $node->bundle(),
-          ]));
-          $response = new RedirectResponse('/');
-          $event->setResponse($response);
+        if (!in_array($node->bundle(), $allowed_types)) {
+          // /i/{nid} redirects through to the aliased URL on www.drupal.org.
+          $legacy_url = 'https://www.drupal.org/i/' . $node->id();
+          if ($this->currentUser->hasPermission('bypass node access')) {
+            $this->messenger->addWarning(t('%type is not fully migrated to new.drupal.org, this is an admin-only preview. <a href=":url">View on www.drupal.org</a>', [
+              '%type' => $node->bundle(),
+              ':url' => $legacy_url,
+            ]));
+          }
+          else {
+            $response = new TrustedRedirectResponse($legacy_url);
+            $event->setResponse($response);
+          }
         }
       }