This makes the per app "Notifications" toggle in g-c-c work.
This needed some tweaks to the
source_id used for the
PhoshNotificationBanner which in turn requried us to keep the
desktop_id around too.
I'll unwip after brushing up the tests and more testing (mostly cobbled this together during the GTK BoF)
Signed-off-by: Guido Günther firstname.lastname@example.org