Create broadcast event

A BroadcastEvent records a single unit of work within a Luma broadcast flow, a bulk outbound messaging campaign sent to many patients at once (for example a recall or announcement uploaded as a spreadsheet). Each event tracks either a review action taken on the flow or the processing of one row or patient, including its current step (message queued, sent, failed, or skipped), any error encountered, and links to the associated patient and appointment.