Inline Product Checkout (Without Pre-Created Product)

I want to be able to call POST /v1/checkouts with inline product details (name, price, currency, billing_type) without needing to create a product beforehand. This would help because sellers don't always have their Creem account connected when creating products in our platform (Linklify), leading to sync issues. It also adds complexity to manage products across both systems and fills up the seller's Creem catalog with items that only exist in Linklify. Stripe handles this with Payment Intents, and a similar "ad-hoc" checkout in Creem would be a big improvement.