Clean up unused application records (#24871)

app/lib/application_extension.rb

@@ -4,6 +4,8 @@ module ApplicationExtension
   extend ActiveSupport::Concern
 
   included do
+    has_many :created_users, class_name: 'User', foreign_key: 'created_by_application_id', inverse_of: :created_by_application
+
     validates :name, length: { maximum: 60 }
     validates :website, url: true, length: { maximum: 2_000 }, if: :website?
     validates :redirect_uri, length: { maximum: 2_000 }