Self-service cancellations

[jace]

Boxoffice should allow self-service cancellations without requiring the user to go through support. Cancellations should be a part of the ticket management page.

[shreyas-satish]

Should the assignee of a ticket be allowed to cancel a ticket or should this ability be restricted to the buyer? I think the attendee should be allowed to cancel the ticket. Here's a possible workflow:

1. Buyer/Assignee clicks on the 'Request to cancel' button, which is displayed on the ticket.
2. This results in an email with a cancellation link (with token which expires in 10 minutes) that is sent to both the buyer and the attendee.
3. The link takes the buyer/attendee to a page which asks them for a confirmation, and cancels the ticket on confirmation.