feat(11.1-04): add the Backend section, the remaining Services pages and the concept map links

- docs/backend: admin controllers, forms, lists and filters, relation
  manager, users and permissions, settings, partials and widgets, admin SPA
- docs/services: storage, outbound HTTP, realtime, Web Push, search, parity
  testing and the Frontend and AJAX (not provided) page
- Examples for cabana (with testdata/docs YAML), fetchguard, lighthouse and
  its centrifugo driver, flare, beachcomber and typesense, tide; lighthouse
  and beachcomber TestDocs* regions run on their Postgres harnesses
- concept map rows link their guide pages and the not-provided rows the
  Frontend and AJAX page; index lists Backend, Database and Services
- TestDocsRequiredPages asserts the D-08 section order

modules/cabana/testdata/docs/controllers/posts/config_form.yaml

@@ -0,0 +1,10 @@
+name: acme.blog::lang.posts.form
+form: ~/plugins/acme/blog/models/post/fields.yaml
+modelClass: Post
+defaultRedirect: acme/blog/posts
+create:
+    redirect: acme/blog/posts/update/:id
+    redirectClose: acme/blog/posts
+update:
+    redirect: acme/blog/posts
+    redirectClose: acme/blog/posts