Prevent owning product multiple times

I'd like a way to prevent a customer from purchasing a product they already own again — whether by accident or otherwise.

Why this matters:

• This directly ties into the ownership-based discount request — without this, there's no way to guarantee a discount (or promo) tied to ownership only gets used once per item. https://feedback.jinxxy.com/p/ownership-based-discounts

• Ideally this would be enforced automatically at checkout (e.g. block or warn if the customer's account/email already shows a completed purchase of that item), rather than something I have to manually police.