Capture of Job posting source

Summary

How do we record on a job requisition which job-boards etc we have used to advertise the job?

Content

How do we record against a job requisition what job-boards or other media sources we have posted the job requisition to?
my customer wishes to report on the effectiveness of media sources such as job boards for a particular requisition and does not use a job-board aggregator.

• I know that we can add an identifier into the url of the apply link we send to a job-board in order to capture the applicants source 
• I know we can therefore report on those job-boards/sites through which an applicant has applied