Subscription Server Notification: PRICE_INCREASE_CONSENT

WWDC 2019 session 302 - In-App Purchases and Using Server to Server Notifications introduced a PRICE_INCREASE_CONSENT notification, and accompanying price_increase_effective_date attribute in the notification payload. This notification does not appear to have made it into the docs though, so I'm wondering if this notification was scrapped, or if it is actually available and insufficiently documented. If the latter, I'd like to know where in the body I can expect to find the price_increase_effective_date attribute, and which format that date is in. Thanks for any insight!