curl --request POST \
  --url https://api.referralful.com/v1/campaigns \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "name": "<string>",
  "url": "<string>",
  "commission_percent": 123,
  "commission_amount_cents": 123,
  "days_before_referrals_expire": 123,
  "minimum_payout_cents": 123,
  "max_commission_period_in_months": 123
}
'

{
  "id": "<string>",
  "object": "campaign",
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "name": "<string>",
  "url": "<string>",
  "private": true,
  "commission_percent": 123,
  "commission_amount_cents": 123,
  "commission_currency": "<string>",
  "minimum_payout_cents": 123,
  "days_before_referrals_expire": 123,
  "days_before_commissions_are_due": 123,
  "max_commissions": 123,
  "max_commission_period_in_months": 123
}