Improve registrar area linked user switch

- Introduce profile
- Move linked users to profile
- Use PUT

#599

config/routes.rb

@@ -43,11 +43,11 @@ Rails.application.routes.draw do
       post 'sessions' => 'sessions#create'
       post 'id' => 'sessions#id'
       post 'mid' => 'sessions#mid'
-      get 'switch_user/:id' => 'sessions#switch_user'
       delete 'logout', to: '/devise/sessions#destroy', as: :destroy_user_session
     end
 
-    get 'current_user/switch/:new_user_id', to: 'current_user#switch', as: :switch_current_user
+    put 'current_user/switch/:new_user_id', to: 'current_user#switch', as: :switch_current_user
+    resource :profile, controller: :profile, only: :show
 
     resources :domains do
       collection do