* BIP21: Uppercase addresses only in QR, not in payment URL
The uppercased address/BOLT11 should only be used for the QR code, the payment URI for the link should stay as it is.
References:
- #2110
- https://bitcoinqr.dev/
* Improve comments
* Add comments step by step
* Ensure correct delimiter
Co-authored-by: nicolas.dorier <nicolas.dorier@gmail.com>