Adding Sidekiq for background processing (firstly just of mailers)

config/routes.rb

@@ -1,4 +1,10 @@
+require 'sidekiq/web'
+
 Rails.application.routes.draw do
+  authenticate :user do
+    mount Sidekiq::Web => '/sidekiq'
+  end
+
   use_doorkeeper do
     controllers applications: 'oauth/applications'
   end