I want to implement a custom notification message per product or collection. As such, when product x is purchased the system sends an email with relevant details about that product x, and when product y is purchased another message is sent with relevant details.

Could you guide me to the right way to do so?

I could have added a message property to the document type allowing site editors to type the message body (same like in OrderConfirmation.cshtml). However, I then struggle to access such property in methods like (AddBasketItem, or even in the trigger and monitor).

Please advise.