feat(event available/sold out): Promoter can mark event as sold out or available

On the event page, promoter can choose to mark the event as "sold out" using the status field or as "published". Only published event can be marked as sold out if promoter thinks he cannot handle all the people available.

config/routes.rb

@@ -81,6 +81,7 @@ Rails.application.routes.draw do
         patch :unpublish
         patch :cancel
         patch :mark_sold_out
+        patch :mark_available
         post :duplicate
       end