NUT-05: Melting tokens without blocking

[callebtc]

Currently, calling POST /melt is blocking until either the Lightning invoice succeeds or fails. This is not necessary anymore because we now have a new pending state in the POST /check response (see here: https://github.com/cashubtc/nuts/pull/21).

POST /melt should have an option to immediately return. I'm unsure what the best way would be to spec this out.

Input is very much appreciated.

Options:

• POST /melt?blocking=false with a URL param
• PostMeltRequest with optional blocking: false field in json
• New endpoint a la POST /melt/async
• Use the HTTP Header Prefer: respond-async

[gohumble]

Have you thought about using the HTTP Header Prefer: respond-async from RFC7240?

[callebtc]

Have you thought about using the HTTP Header Prefer: respond-async from RFC7240?

I didn't know about that, will add it as a fourth option :)