curl --request POST \
  --url https://api.sprucecollective.co.uk/raffles/checkout \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "entries_count": 25,
  "raffle_id": "<string>",
  "payment_method": "<string>"
}
'

{
  "amount": 123,
  "checkout_url": "<string>",
  "currency": "<string>",
  "entries_count": 123,
  "order_id": "<string>",
  "signature": "<string>",
  "timestamp": 123
}