New webhook to notify when a billing attempt is 3DS-challenged

External apps can now subscribe to a webhook event to be notified when a financial institution challenges a subscription billing attempt charge. This update is in accordance with 3-D Secure.+

The webhook event will trigger a message to be published on the subscription_billing_attempts/challenged topic. To use the topic, an app requires the own_subscription_contracts access scope.

For more information, visit the REST Admin API Webhook documentation.