LINK-1799 | Cancel signups on event deletion or cancellation

[harriris-vincit]

Description

This PR implements the following three requirements:

• When an event that has a registration is soft-deleted or cancelled, the related registration's signups and signup groups need to be cancelled and their contact persons notified.
• When a sub-event of a super event is soft-deleted or cancelled, only event cancellation notifications should be sent and the signups should remain if the registration is linked to the super event only.
• Payments should be cancelled or refunded in case signup and signup groups cancellations are performed.

Closes

LINK-1799