I don't understand apple store server to server notification

Hello,

I'am trying to validate a new app from apple.

I have configured sandbox url and production url for server to server apple store notification.

I have created subscriptions product id, but there are no validated yet by apple.

When I upload my app to testflight, I can't test sandbox notification cause the product id are not available, on local xcode with storekit file I got my product Id but I don't receive notification.

So my question is how can I test there thing. I have to produce fake product id ? I'm lock its very complex process, I don't understand.

I tried to send my app like that for verification but the team told me to use receipt, but its deprecated and notification webhook is better for me.

What is the good order, validate my subscription product ID then test ? what is the good steps. Apple seems to don't want validate my subscription product ID I'm lock..

I don't understand apple store server to server notification
 
 
Q