I should be able to define multiple Shared Invites for a given Role

(User Story, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Security
Summary: The current approach is arguably broken, since once you revoke an Invite, you can never use that Role for invites again.
Also, the current approach doesn't allow for fine-grained permissions on the invite itself, such as requiring recipients to become Querki Users.
The fix is to make Shared Links a subsidiary Thing linked to the Role, instead, and allowing any number of Shared Links for a given Role.