Defines a webhook rule to an external server. The callback URL will receive a POST request with the related object's (e.g. Purchase for purchase.* webhooks) data in body when any of the events (see the description of events field below) it is configured to listen for are triggered. The payload object will additionally include an "event_type" field to indicate which event type (see the Webhook.events field) triggered the webhook.

Note that, as well as with the rest of dataset, test and live Webhooks are separate; test webhooks will not handle events caused by live Purchases, and vice-versa.