In order to create single-use links you need edit permissions, not read permissions

The proper way to address this would have been to implement a Sufia::Ability module and add an ability for SingleUseLink objects, but that proved pretty complicated and would potentially impact everyone who is using Sufia in annoying ways, so I just went with the simple route - changing the hard-coded :read to :edit.  If someone has suggestions, I'm listening. :ear: