Merge branch 'cache-broadcast-message-current' into 'master'

Cache BroadcastMessage.current. Fixes #12770



See merge request !2633

app/models/broadcast_message.rb

@@ -26,8 +26,10 @@ class BroadcastMessage < ActiveRecord::Base
   default_value_for :font,  '#FFFFFF'
 
   def self.current
+    Rails.cache.fetch("broadcast_message_current", expires_in: 1.minute) do
       where("ends_at > :now AND starts_at <= :now", now: Time.zone.now).last
     end
+  end
 
   def active?
     started? && !ended?