Ask for confirmation when a user cancels his participation in an event

[mconf-daileon]

---

Author Name: Leonardo Daronco (Leonardo Daronco) Original Redmine Issue: 1523, http://dev.mconf.org/redmine/issues/1523

---

There a route for users to cancel their participation in an event, a URL in the format: http://server.com/participant_confirmations/h2e7h782/cancel. When accessed (via GET), this route will cancel the user's participation in the event.

It's good that it is a GET request, so it can be sent in an email and the user can simply click on it. But it should at least require confirmation before cancelling the participation. The route that cancels the participation could be modified to render a page with a message and a button the user has to click to confirm the cancellation (similar to the page to accept/decline join requests). Clicking on this button would send the user to another route via POST/DELETE and actually cancel the participation.