You can now try the implementation out with a demo form on the default server with the latest ODK Collect v1.25 beta!
Documentation will be published by the time the release goes out. XLSForm support will come after. In the mean time, the identify-user spec and track-changes-reasons spec are available. To add these options to your XLSForms, you can add columns bind::odk:identify-user and put true in the audit row and/or bind::odk:track-changes-reasons and put on-form-edit in the audit row.