Update actions/checkout to v4

…aginate gem

Update add_pagination_links.md to add specific instruction for will_paginate gem

Instead of referencing ActionController::TestCase directly during boot,
we can use a lazy load hook to apply our mixins if it is loaded later.

The action_controller_test_case load hook was added in Rails 5.1, and
the run_once option was added in Rails 5.2. I've left the behaviour
unchanged for older Rails versions where they're not available.

…est_case

Don't force ActionController::TestCase to load

Fix cant modify frozen Hash error due to rails changes

Support Rails 8