So I'm wondering, if we build a new sales channel app and let the app decide a new price for each line item on its own platform, will this Checkout API support that?
Merchants usually want to sell products on different sales channels and, since the cost is different on different platforms (such as facebook, instagram, pinterest, or a new one), they want to sell a different price on different channels. If the new channel wants shopify to handle the payment processing it should send back to shopify (by API call) the new Checkout object including new line items and new price for each line. That's where the question is from. Can some shopify staff explain this question to developers as the official docs doesn't mention this. :)