同じ OmniAuth provider を１つのアプリで複数使いたい

path_prefix と callback_path を変えて複数登録すればいい

Rails.application.config.middleware.use OmniAuth::Builder do
  privider :twitter, 'x_key', 'x_secret', path_prefix: '/auth/xxx', callback_path: '/auth/xxx/twitter/callback'
  privider :twitter, 'y_key', 'y_secret', path_prefix: '/auth/yyy', callback_path: '/auth/yyy/twitter/callback'
end