Inform clients about suspend

Since there is "resume", and there is a moment when resuming that
domain might still be suspended, or event suspending a domain on
purposed, allow clients to know the domain state.

Author: ben-grande

qubes/vm/qubesvm.py

@@ -447,6 +447,15 @@ class QubesVM(qubes.vm.mix.net.NetVMMixin, qubes.vm.LocalVM):
             :param subject: Event emitter (the qube object)
             :param event: Event name (``'domain-unpaused'``)
 
+        .. event:: domain-suspended (subject, event)
+
+            Fired when the domain has been suspended.
+
+            Handler for this event may be asynchronous.
+
+            :param subject: Event emitter (the qube object)
+            :param event: Event name (``'domain-suspended'``)
+
         .. event:: domain-resumed (subject, event)
 
             Fired when the domain has been resumed from suspend.
@@ -1771,6 +1780,7 @@ async def suspend(self):
             self.libvirt_domain.pMSuspendForDuration(
                 libvirt.VIR_NODE_SUSPEND_TARGET_MEM, 0, 0
             )
+            await self.fire_event_async("domain-suspended")
         except libvirt.libvirtError as e:
             if e.get_error_code() == libvirt.VIR_ERR_OPERATION_UNSUPPORTED:
                 # OS inside doesn't support full suspend, just pause it