LUD21 gets update and needs support in GUI

[arbadacarbaYK]

LUD21 update is about an optional Pin before (BoltCard) withdrawals or payments above a certain amount are allowed.
4 digits pin, 3 retries before link/card invalidation seems consensus.
lnurl/luds#200

Note that there are virtual BoltCards now, which might spread way faster than physical cards.

Pin should be asked for if included in callback at least on tpos.
Show descriptive errormsg if pin is put in wrong or link is invalidated.
Its already implemented here for tpos reference https://github.com/boltcard/bolt-card-pos

More detailed

1. The POS/Wallet scans the NFC device and makes a call to the LNURLw
2. If the response includes the pinLimit field AND the value that the POS wants to withdraw is equal or above the pinLimit value, the POS must aquire a PIN (by whatever means) from the payer and add it as URL parameter to the second callback when submitting the invoice to the service.

Also to do :

• Configurable in the Boltcard extension per card (not UID cause random-UID is planned)
• Invalidate (deactivate) card on 3 failed pin-retries

I do not see a similar urgent use case for normal voucher + pin atm.