put
https://api.sintalk.com.br/v3/campaigns//schedule
Set the instant the campaign launches itself at. scheduled_at must be strictly in the future, otherwise 422 unprocessable_entity. The campaign must be draft, error, or already scheduled — that last case reschedules it — otherwise 409 conflict.
The campaign moves to scheduled and, at scheduled_at, launches exactly as an explicit launch would: same snapshot rule, same running to completed path. A schedule that comes due while a bulk contact load is still running on the target list waits for the load, and the campaign moves to error if it has not finished in time.