Comment 4 for bug 1969783

I'm lacking such an API for constructing the value for QGuiApplication::setDesktopFileName (which is used for window association on Wayland, com.canonical.Unity counter via QGuiApplication::setBadgeNumber and whatnot via third-party Qt libraries) and for io.snapcraft.Settings.SetSub default-url-scheme-handler (marking the app as the default handler for an URL scheme). The former needs actual .desktop file name (SNAP_INSTANCE_NAME + app name) while the latter accepts just app name.