namespaceing devise_for user but not current_user helper

route.rb

namespace :api do

 #when devise_for is called in a namespace, the helpers and controller filters change
 #:singular => :user  added so we can use current_user instead of current_api_user. 
 #And before_filter authenticate_user! instead of authenticate_api_user!
 #https://github.com/plataformatec/devise/issues/412
    #devise_for :users, :singular => :user, skip: :all

    get :csrf, to: 'csrf#index'
    resources :users
    resources :sessions
    #post "/sign_in"    => "sessions#create"
    delete "/signout" => "sessions#destroy"
  end