How do I retain cards using Express?

When using Spreedly Express, the ability to auto retain cards is disabled by default when creating a payment method.  The API call will only cache the payment method for a short period of time, then auto-redact it.  We do this to prevent malicious users from storing additional cards on your behalf. 

Instead, to auto retain cards with Express, create the payment method then use the Verify call against your gateway, and set the retain_on_success parameter to true. The card will only be stored in your vault if the call to verify is successful, meaning the card is real and can be charged.