Support LNURL withdrawals

[fiatjaf]

https://github.com/btcontract/lnurl-rfc/blob/master/spec.md#3-withdrawing-funds-from-a-service

It's specially useful in these days post 0-sat invoice exploit.

It requires only that when a QR code starting with lnurl is found you

1. decode it to get an https://... URL;
2. GET that URL;
3. Use the response parameters to show an invoice prompt to the user like https://lightning-wallet.com/ does -- or just use the defaults and make the invoice automatically without user interaction as t.me/lntxbot does;
4. Send the invoice back to the URL given also as a parameters.

That will generally trigger the service to pay the invoice automatically.

[fiatjaf]

I can work on that if and when you decide it's a good addition.

[Darth-Coin]

Not sure if is OK to add a comment to this, but I have a problem with LNURL Pay in Spark wallet. In my case was this, using mobile and desktop Spark, vers 2.1.4 and c-LN 0.9..01. Tried to pay a LNURL from for example https://lntxbot.bigsun.xyz/@Lairebyireneapolo Scanning the QR, didn't get it. Pasting the code, returned the error: invalid bolt11 unknown chain url

I thought that is something wrong with my Spark so I tried with other wallets (BlueWallet and BLW), both worked and paid. If you consider that I should put this as a separate issue please let me know.

[bitpaint]

Not sure if is OK to add a comment to this, but I have a problem with LNURL Pay in Spark wallet. In my case was this, using mobile and desktop Spark, vers 2.1.4 and c-LN 0.9..01. Tried to pay a LNURL from for example https://lntxbot.bigsun.xyz/@Lairebyireneapolo Scanning the QR, didn't get it. Pasting the code, returned the error: invalid bolt11 unknown chain url

I thought that is something wrong with my Spark so I tried with other wallets (BlueWallet and BLW), both worked and paid. If you consider that I should put this as a separate issue please let me know.

same here. spark with c-lightning don't work. qrcode from etleneum- returned the error: invalid bolt11 unknown chain url

[shesek]

Yes, LNURL is not yet supported. I would very much like to add support though and hope to find some time to work on this in the near future. A PR would be greatly appreciated if someone's up for it. :)

(@fiatjaf sorry, I somehow missed your message about this until now. but definitely yes)