Add a "waiting list" status for registrations #32
Description
Possible status for registrations are only "accepted", "pending" or "deleted" (https://github.com/thewca/wcif/blob/master/specification.md#registration). Since the registration workflow has been changed, we now have a new status on the website which is "waiting list". This should be added in the WCIF as well. Right now all "pending" and "waiting list" registrations are exposed as "pending" (cf this issue: thewca/worldcubeassociation.org#12271)