paymentSessionPending
Change a payment session status to pending.
Upon receiving the response from the `PaymentSessionPending` mutation,
you must redirect the customer back to Shopify, using `redirectUrl` in `nextAction`.
Upon completion, pending payments must be finalized into either a successful or failed state using
the `paymentSessionResolve` or `paymentSessionReject` mutations.
Both `sale` and `authorization` payments can be marked as pending.