ActiveAdmin does not work when `permanent_connection_checkout` is disallowed (v3 / v4, Rails >= 7.2)

[tagliala]

It is when config.active_record.permanent_connection_checkout = :disallowed config is used. Which is a good idea when using fibers, as there can be many more fibers than threads and then dry up the db pool

Try and load the admin users page and see the exception.

Originally posted by @henrikbjorn in #8474 (comment)

Expected behavior

ActiveAdmin works

Actual behavior

ActiveRecord::ActiveRecordError in Admin::CommentsController#index

Called deprecated `ActiveRecord::Base.connection` method.
Either use `with_connection` or `lease_connection`.

How to reproduce

1. Clone demo.activeadmin.info
2. Add config.active_record.permanent_connection_checkout = :disallowed to config/application.rb
3. Go to http://localhost:3000/admin/comments

More information

Old PR addressing this issue #8474

[mmogy8313-del]

ActiveRecord::ActiveRecordError in Admin::CommentsController#index

Called deprecated ActiveRecord::Base.connection method.
Either use with_connection or lease_connection.