Fix 'found unpermitted parameter: :orders' dynamically

Hard coding :orders here gets the tests to pass, but is naive. Unless the intention is to override the sanitized_order_params for each app in the admin/application_controller.rb file and manually specify every new resource that is added?

Instead, what is working for me is a dynamic list of any possible has_many resource names in the system as shown in this PR. Lack of specifying these permitted params will result in the following error messages.

ActionController::UnpermittedParameters in Admin::Customers#show

found unpermitted parameter: :orders