> the receiver can easily check if a specific message was already received
It seems like you're conflating exactly-once delivery with exactly-once processing. Your proposed solution is only necessary _because_ we can't have exactly-once delivery as TFA states.
I don't agree with that contrived definition of delivery. As a developer, what I care about is delivery of the message to my function/handler. E.g. so that I can store it in my local database/store on the receiver side exactly once and ultimately show it to the user exactly once. Definitely possible.
We're excited to build an API for Payment Links soon. Drop me a note at jackerman@stripe.com and happy to add you to the early access beta when we launch!
It seems like you're conflating exactly-once delivery with exactly-once processing. Your proposed solution is only necessary _because_ we can't have exactly-once delivery as TFA states.