Tracking when an introductory offer ends

Hi,

I want to track on backend side when a trial subscription (introductory offer) just ends and Itunes automatically initiates billing against the user's credit card.

https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/StoreKitGuide/Chapters/Subscriptions.html

Does Itunes send any event when the introductory offer ends? in this case, what notification type does Itunes send?
Kind regards,