The notification types to subscribe to. If not provided, the webhook will be unrestricted, and a notification is sent for every notification type. If the wildcard (*) or any combination of the wildcard and a set of notification types is provided, the webhook will also be unrestricted. If a set of notification types are provided, the webhook will be restricted. The restricted status of the webhook is returned in the response object. Each category of notification types also has a wildcard, which will restrict to all notification types from that category.