Add comment probably on expectation based implementation searching

app/models/dunlop/target_file_model.rb

@@ -1,6 +1,8 @@
 module Dunlop::TargetFileModel
   extend ActiveSupport::Concern
   extend Memoist
+  # Looking for the ::Job implementation? This is implemented in the to_prepare engine statement
+  #   lib/dunlop/engine.rb
   PAPERCLIP_S3_HEADERS = Proc.new do |attachment|
     if attachment.persisted?
       {}