curl --request POST \
  --url https://api.example.com/cabinet/landing/{slug}/purchase \
  --header 'Content-Type: application/json' \
  --data '
{
  "tariff_id": 123,
  "period_days": 123,
  "contact_type": "<string>",
  "contact_value": "<string>",
  "payment_method": "<string>",
  "is_gift": false,
  "gift_recipient_type": "<string>",
  "gift_recipient_value": "<string>",
  "gift_message": "<string>"
}
'

{
  "purchase_token": "<string>",
  "payment_url": "<string>"
}