Move before action for regenerate_api_key

Raising for missing callback actions is a new default in Rails 7.1. Therefore
a callback that is defined by an extended concern will cause a failure if the
action is not defined. The `regenerate_api_key` only exists for external user
admin so the callback needs to be moved from the concern to the controller.

app/controllers/concerns/provider_admin_concern.rb

@@ -2,7 +2,7 @@ module ProviderAdminConcern
   extend ActiveSupport::Concern
 
   included do
-    before_action :set_provider, only: %i[show edit update regenerate_api_key]
+    before_action :set_provider, only: %i[show edit update]
   end
 
   private

app/controllers/external_users/admin/providers_controller.rb

@@ -3,6 +3,8 @@ module Admin
     class ProvidersController < ExternalUsers::Admin::ApplicationController
       include ProviderAdminConcern
 
+      before_action :set_provider, only: :regenerate_api_key
+
       def regenerate_api_key
         @provider.regenerate_api_key!
         redirect_to external_users_admin_provider_path(@provider), notice: t('.notice')