GNotification: Add support for getting notification server capabilities
Not every notification server support notification action. As a result it causes undesired behavior for third party developers using GNotification. It would be nice if GNotification has native api for checking server capabilities without making dbus calls to org.freedesktop.Notification.
Libnotify already supports this kind of check,
https://developer.gnome.org/libnotify/unstable/libnotify-notify.html#notify-get-server-caps
Thanks.