To do testing of flatpaks, we need another target set up in staging koji

stg-koji add-tag f28-flatpak
stg-koji add-target f28-flatpak-candidate f28-build f28-flatpak

This should do for testing for now - I'm not sure if the final setup in production will be quite like this. (It's not entirely clear if a separate f28-flatpak destination is desirable - we could just use f28-container.)

@cverna - once this target is created, we can try:

koji-containerbuild -p staging flatpak-build f28-flatpak-candidate git://pkgs.stg.fedoraproject.org/modules/banner#origin/master --git-branch=master

and see what happens :-)