Payload for POST /email-notifications (saves a draft).
Audience filter as sent by the UI and stored (denormalised) on the email_notifications row. Validator guarantees the selector fields match mode so the resolver doesn't have to second-guess the input.
Successful Response
Wire-format for a notification record. Mirrors the TS EmailNotification interface. from_name / from_address are returned on every response so the detail page can show recipients what sender was used — but they're always the configured operational sender.