cubicweb-cmt #1381992 handle non-public shoppingitemtypes [validation pending]

in order to register speakers and journalists, we need shoppingitemtypes that are not available to the general public.

prioritynormal
typeenhancement
done in0.4.0
load0.000
load left0.000
closed by#086d48a3affe [packaging] depend on shoppingcart >= 0.4.0 to have items_available_to (closes #1381992)