Schedule campaign

curl --request POST \
  --url https://app.usesend.com/api/v1/campaigns/{campaignId}/schedule \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "scheduledAt": "<string>",
  "batchSize": 50000
}
'

{
  "success": true
}