do not require gems to sublcass Application* classes

ruby/rubocop-for-gem.yml

@@ -27,6 +27,18 @@ Naming/FileName:
 
 
 # BEGIN Rails
+# allow gem models to subclass ActionController::Base instead of ApplicationController
+Rails/ApplicationController:
+  Enabled: false
+
+# allow gem jobs to subclass ActiveJob::Base instead of ApplicationJob
+Rails/ApplicationJob:
+  Enabled: false
+
+# allow gem mailers to subclass ActionMailer::Base instead of ApplicationMailer
+Rails/ApplicationMailer:
+  Enabled: false
+
 # allow gem models to subclass ActiveRecord::Base instead of ApplicationRecord
 Rails/ApplicationRecord:
   Enabled: false