curl --request POST \
  --url https://api.pickfu.com/v1/surveys/{id}/respondents \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "respondentsAmount": 500,
  "preview": false
}
'

{
  "success": true,
  "preview": true,
  "data": {
    "currentRespondents": 123,
    "newRespondents": 123,
    "additionalRespondents": 123,
    "costInCredits": 123,
    "creditBalance": 123,
    "canPayWithCredits": true,
    "id": "<string>",
    "respondentsAmount": 123,
    "state": "<string>"
  }
}