lnurl/lnaddress qr compatibility

[vv01f]

date/commit-height: 2023-04-15 2197b53 for version reference

relates to #444

problem: currently the printable static qr is a website url with parameter for lnurl in uppercase encoding.
this results in the qr not being accepted by lightning wallets and quite some advanced users and an additional qr reader being necessary to fix issues. waiting for standardization might hurt users and thus adoption in the meantime.

problems:

• uppercase
• website url
• lnurl only

measures for better wallet compatibility and usablility I imagine with e.g.

• band together with other (esp. wallet) teams to level up on interoperability
• show the encoded text underneath the QR Code for human readability in doubt
• make it lowercase, I would not count on other implementations mitigating this (known fail with samourai wallet encoding BC addresses uppercase leading to problem for users not aware of this)
• option for lnurl only
• option for lnaddress only
• option for bip 20 uri with fallback parametersfor lnurl/lnaddress
• (future) option for bolt12
• don't rely on clearnet only (as openoms already suggested in Support paying LNURLpay codes using Tor #444)
• add list of wallets tested as compatible with the qr (app symbols might suffice) to the print page

wallet tests

Only scanning the QR as is with wallets available to verify if I can pay the lnaddress included in the lnurl as a parameter of the webwallet.
Not validated if the payment is actually happening.
My list is sorted by likelyhood (most likely first) the wallet implementation is used, Android only.

Wallet	Result
Wallet of Satoshi	fails, no error message
muun	error: this is not a btc address, helpful message shows the scanned text
Phoenix	error: unknown data, no helpful error message
Blue Wallet	ok
Breez	ok
Zeus	ok
Zap	offers to open the link but fails and crashes