Add webinar registrants to three-day reminder mailing list

Webhook webinar signups aren't added to lists, causing outreach gaps and missed reminders. Add registrants to a three-day reminder list so campaign managers send pre-event emails on time.

Overview

When webinar signups arrive via webhook they can sit outside your mailing system and miss reminder emails. This flow captures each signup and stages it for the three-day reminder list so campaign managers can send pre-event emails on schedule, improving attendee readiness ahead of the webinar.