Add event attendee to matching shared calendar entry

Event registration updates don’t always reach the shared calendar, so hosts lack attendee visibility. Adds confirmed attendees to the matching calendar event so hosts and staff see the list before start time.

Overview

When registration systems mark attendees confirmed but calendars lag, hosts scramble for attendee lists and access prep. This flow finds the matching calendar event and inserts confirmed attendees, giving hosts the visible roster ahead of start time and reducing last-minute access issues.