I have a full working and hosted external frontend. I wanted to use the shopify for checkout only and viewing order details on dashboard. The problem is my product variants have prices as fixed percentage of original product. Like option1 = A then 120% of price, option1 = B is 150% of price etc. and so on. So are there any external apps for this ? I found most apps out there are embeddable but I have a hosted website which I want to migrate to shopify, so I don't want ui components to embed rather endpoints like storefront api.