Merge pull request rails#51533 from p8/guides/advanced-active-record

Move "Advanced Active Record" guides to separate section [ci-skip]

Author: p8

guides/source/documents.yaml

@@ -234,6 +234,10 @@
       name: Using Rails for API-only Applications
       url: api_app.html
       description: This guide explains how to effectively use Rails to develop a JSON API application.
+
+-
+  name: Advanced Active Record
+  documents:
     -
       name: Active Record and PostgreSQL
       work_in_progress: true