Issue Summary

Track announcement banner changes in the audit log. Whenever a banner is published or updated, there should be an entry in the log to be able to track changes. 

Steps to Reproduce

• Configure an announcement banner as described on this page: https://confluence.atlassian.com/jirakb/configuring-an-announcement-banner-1217300328.html 
• Check the audit log but there won't be any entries about the banner.

Expected Results

• Record changes to the announcement banner in the audit log. Show before and after like what shows when a user is renamed.

Actual Results

• Changes to the announcement banner are not recorded in the audit log.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available