Feature request: cancel registrations

[PLNReynolds]

We typically have quite a few learners who need to cancer their registrations (often 20%+). Currently they send us an email and we have to go in manually and cancel them. It would be great to be able to allow registrants to un-enroll themselves and automatically free up their spot for the waitlist, etc. Registrant accounts would be great (and reduce the user monotony of filling in personal info over and over for multiple event signups), but a shortcut Matt brainstormed could be access keys delivered via their registration confirmation emails that would let them go back and cancel their (and only their) registration for that event. Or maybe other workflow options that would be better?