check_details should have its own timestamp

check_details should have its own timestamp as it may have been performed asynchronously from the point in time that the evidence was captured, especially if that involved a manual process. Suggest adding the following to check_details :

time: OPTIONAL. Time stamp in ISO 8601:2004 [@!ISO8601-2004] YYYY-MM-DDThh:mm[:ss]TZD format representing when the check was performed.