documentation on HSM Policy (zimbraHsmPolicy)

[xtremetoonz]

We just upgraded our Network Edition install to the latest and greatest (previously on 5.0.16) and I am interested in implementing a HSM policy that not only moves the canned messages, chat, documents, etc but also Junk email per the bug id 19655 (Bug 19655 – Junk mail storage (secondary/HSM volume for Spam messages)). I am not sure even after some extensive searching what the syntax would be to integrate the message:in:junk into the web ui canned string. The bug doc says, "Please see the spec for the zimbraHsmPolicy attribute for more details." but where is that? My searches are coming up empty. Thank you for any help and great job on ZCS to date!