Test sharing with groups

[michielbdejong]

The spec says you can share with a remote user or a remote group.
So far we have only been testing sharing with remote users.

[michielbdejong]

I guess this would not work for the invite flow, because a group can't accept an invite.
But maybe groups that are defined in some AAI could be visible as 'accepted users' at the CS3APIs level?
This could be something to explore in https://github.com/SURFnet/rd-sram-integration/milestone/4 actually -> created a break-out issue for that.