A Checkout Session represents your customer's session as they use Smartpay Checkout to pay for orders or create a token.
The Checkout Session will contain a reference to the Order or Token once created. If your user completes their Smartpay checkout successfully, the Order or Token will be successful.
A Checkout Session needs to be created on your server using a private API key. To begin Smartpay checkout redirect the user to the url returned by the call