[libvirt] [RFC] driver's persistent connection closed event

Hello. I have a question concerning hypervisor driver "persistent connection closed" event mechanics. Currently the only driver that have such a connection (or at least notify of such event) is the remote driver. Accordingly we don't have interface for this event at driver level. Parallels driver actually have a persistent connection. Imagine we have a libvirt connection to parallels driver through remote driver, if parallels internal connection is closed we can catch it in daemon but the only option to notify remote driver of this event would be closing of remote driver to daemon connection which will in turn trigger connection closed event deliver to client. Thus event will be delivered but at cost of forcedly closed connection to daemon. I suspect the described solution have architectural flaws so i suggest move interface of "persistent connection closed" event to driver level which will give us a chance to deliver this event without side effects. We don't need to implement this interface for most drivers and clients could handle this well as in this case "unimplemented" would be a synonym of "have not persistent connection". Alternatively we could silently do nothing if driver does not support this interface so clients would not break.