To share code between the GTK and DBus UI bakcends
see the next commit for details

Signed-off-by: Bilal Elmoussaoui <belmouss@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230619095337.9899-2-belmouss@redhat.com>