[#4604] Timestamp the last caching run

app/models/rate.rb

@@ -80,6 +80,7 @@ class Rate < ActiveRecord::Base
         end
       end
     end
+    store_cache_timestamp('last_caching_run', Time.now.to_s)
   end
   
   private
@@ -121,6 +122,10 @@ class Rate < ActiveRecord::Base
     end
   end
 
+  def self.store_cache_timestamp(cache_name, timestamp)
+    Setting.plugin_redmine_rate = Setting.plugin_redmine_rate.merge({cache_name => timestamp})
+  end
+
   if Rails.env.test?
     public
     generator_for :date_in_effect => Date.today