https://docs.voucherify.io/reference/add-voucher-with-certain-code-to-campaign
https://docs.voucherify.io/reference/add-voucher-to-campaign
https://docs.voucherify.io/reference/create-campaign
https://docs.voucherify.io/reference/delete-campaign
https://docs.voucherify.io/reference/get-campaign
https://docs.voucherify.io/reference/import-vouchers
https://docs.voucherify.io/reference/list-campaigns
https://docs.voucherify.io/reference/update-campaign
https://docs.voucherify.io/reference/add-voucher-with-certain-code-to-campaign