internal/outcome: populate instance metadata for PipeWire

These have similar semantics to equivalent Wayland security-context-v1 fields.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/sppipewire.go

@@ -18,7 +18,12 @@ func (s spPipeWireOp) toSystem(state *outcomeStateSys) error {
 		return errNotEnabled
 	}
 
-	state.sys.PipeWire(state.instance().Append("pipewire"))
+	appId := state.appId
+	if appId == "" {
+		// use instance ID in case app id is not set
+		appId = "app.hakurei." + state.id.String()
+	}
+	state.sys.PipeWire(state.instance().Append("pipewire"), appId, state.id.String())
 	return nil
 }