I'm trying to understand the IAP development process. I created my first Product on App Store Connect and am trying to build my app to use it. However it keeps failing with "Invalid product ID.". From what I've read, this is because the product has not yet gone through review. But what I don't understand is, of course it hasn't gone through review yet, because trying to use it in any capacity fails, even though I'm using a real physical device and using a Sandbox User. Is this the correct workflow? It seems very backwards that I have to submit the product for review, even before I know how it's going to be used. I'm still building the screen for the product page, and haven't even started touching any backend APIs, yet it's asking for screenshots. Am I misunderstanding something here?