curl --request POST \
  --url https://rest-api.smsmngr.com/v1/messaging/url \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "bulk_id": "batch-2026-07-30",
  "filetype": "jsonl"
}
'

{
  "success": true,
  "url": "https://smsmngr-bulk-uploads.s3.amazonaws.com/...&X-Amz-Expires=60..."
}