Form object pattern

優點：

1. 把讓 controller 和 view 的邏輯拆開，讓 form object 負責，符合 single responsibility principle
2. 如果 include active_record 可以享用 validations, errors 和符合 convention 等優點




http://culttt.com/2015/11/04/using-form-objects-in-ruby-on-rails/
https://webuild.envato.com/blog/creating-form-objects-with-activemodel-and-virtus/
https://robots.thoughtbot.com/activemodel-form-objects