Integration with third party checkout providers is not available for SSP applications written in Suitescript 2.0.
For integration with third party checkout providers such as PayPal Express and 3D secure, you need to create request handlers (.ss files) for these providers, and call these handlers from your frontend page (.ssp file). The request handlers should use
proceedToCheckout(), as documented in ShoppingSession Methods. This method must pass checkoutsettings JSON object values as parameters. Note that this method can only be called from a secure (https) scheme. For more details, see: