* @object is not needed
* Remove unneeded dependencies
* Do not call private method
* Prefer #respond_to_missing? over #respond_to?
`#respond_to?` doesn't support `User.settings.method(:method_name)`
* Use find_or_initialize_by instead of
* add annotate to Gemfile
* rails g annotate:install
* configure annotate_models
* add schema info to models
* fix rubocop to add frozen_string_literal
Yamagishi Kazutoshi