Add the SiteName field to the audit struct

[allanrogerr]

This is in preparation for the addition of the SiteName to both internal and external audit logs

[klauspost]

@allanrogerr Please state why. It seems silly to add a property that will be the same for every audit log entry. You already have the deployment ID as a site separator.

It seems like a "sounds nice to have", that just adds bloat.