Decline reason attendees in Events

When an event organizer invites attendees, there is currently no way to enforce a reason when those attendees decline or don't show up. The organizer has no insight into why someone is not attending when its for example an mandatory event.

Reason: For customers in regulated or compliance-driven industries (e.g. VCA-certified companies), mandatory toolbox meetings and safety trainings require documented attendance and justification for absence. Without this feature, organizers must follow up manually, reducing the value of the Events module for these use cases.