"omniauth-facebook" gem을 활용하여 페이스북으로 로그인하기 기능 구현하기!

$ rails g migration add_columns_to_users name provider uid image
      invoke  active_record
      create    db/migrate/20140601051431_add_columns_to_users.rb
$ rake db:migrate
== 20140601051431 AddColumnsToUsers: migrating ================================
-- add_column(:users, :name, :string)
   -> 0.0025s
-- add_column(:users, :provider, :string)
   -> 0.0002s
-- add_column(:users, :uid, :string)
   -> 0.0002s
-- add_column(:users, :image, :string)
   -> 0.0002s
== 20140601051431 AddColumnsToUsers: migrated (0.0033s) =======================

참고페이지:

https://github.com/plataformatec/devise/wiki/OmniAuth:-Overview