Constant TRACK_PROPERTIES 

const TRACK_PROPERTIES: &str = "Track Properties are populated in TRACK_STATUS_OK; they are empty \
                                in PUBLISH_OK, REQUEST_UPDATE_OK, SUBSCRIBE_NAMESPACE_OK and \
                                PUBLISH_NAMESPACE_OK. If an endpoint receives Track Properties in \
                                one of these messages it MUST close the session with a \
                                PROTOCOL_VIOLATION.";