curl --request POST \
  --url https://api.sprucecollective.co.uk/rewards/referrals \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "referee_user_id": "<string>",
  "referral_code": "<string>"
}
'

{
  "created_at": "<string>",
  "id": "<string>",
  "is_cancelled": true,
  "is_completed": true,
  "referee_user_id": "<string>",
  "referral_code": "<string>",
  "referrer_user_id": "<string>",
  "site_id": "<string>",
  "status": "<string>",
  "updated_at": "<string>"
}