Lightning / On-chain -> Receive: inconsistency of data (lower/upper case and prefix)

[myxmaster]

Describe your enhancement idea

When creating invoices (or on-chain addresses or lightning addresses) we always have 3 representations of that data:

• QR data
• Displayed text
• Copied data

For each data representation, we need to decide if we need prefixes (lightning: or bitcoin:) and determine casing (all uppercase, all lowercase, or mixed casing [case sensitive]).

Casing:

• QR data should be all uppercase (leads to a smaller QRs / requires fewer bits per character).
  • Exception 1: Mixed case for on-chain legacy and nested SegWit addresses (those are case sensitive)
  • Exception 2: LN addresses are ok lowercase (not much data anyway).
• Displayed text and copied data should be all lowercase because that is easier to read.
  • Exception: Mixed case for on-chain legacy and nested SegWit addresses (those are case sensitive)

Prefixes:

• QR data: Prefixes everywhere
• Displayed text and copied data:
  • We need prefixes for unified invoices
  • We do not need prefixes for lightning invoices
  • We need prefixes for on-chain invoices with amount (lightning->receive->on-chain)
  • We do not need prefixes for lightning addresses
  • We do not need prefixes for on-chain addresses (on-chain->receive)

Right now we have:

lightning -> receive -> unified (SegWit/Taproot)

• QR data uppercase ✔️, with prefixes ✔️
• displayed text uppercase ❌, with prefixes ✔️
• copied data uppercase ❌, with prefixes ✔️

lightning -> receive -> unified (Nested SegWit)

• on-chain part
  • QR data mixed case ✔️, with prefix ✔️
  • displayed text mixed case ✔️, with prefix ✔️
  • copied data mixed case ✔️, with prefix ✔️
• lightning part
  • QR data uppercase ✔️, with prefix ✔️
  • displayed text uppercase ❌, with prefix ✔️
  • copied data uppercase ❌, with prefix ✔️

lightning -> receive -> lightning

• QR data uppercase ✔️, with prefix ✔️
• displayed text uppercase ❌, with prefix ❌
• copied data lowercase ✔️, without prefix ✔️

lightning -> receive -> on-chain with amount (SegWit/Taproot)

• QR data uppercase ✔️, with prefix ✔️
• displayed text uppercase ❌, with prefix ✔️
• copied data uppercase ❌, with prefix ✔️

lightning -> receive -> on-chain with amount (Nested SegWit)

• QR data mixed case ✔️, with prefix ✔️
• displayed text mixed case ✔️, with prefix ✔️
• copied data mixed case ✔️, with prefix ✔️

lightning -> receive -> on-chain without amount (SegWit/Taproot)

• QR data uppercase ✔️, with prefix ✔️
• displayed text uppercase ❌, with prefix ❌
• copied data lowercase ✔️, without prefix ✔️

lightning -> receive -> on-chain wihtout amount (Nested SegWit)

• QR data mixed case ✔️, with prefix ✔️
• displayed text mixed case ✔️, with prefix ❌
• copied data mixed case ✔️, without prefix ✔️

lightning -> receive -> ln-address

• QR data lowercase ✔️, with prefix ✔️
• displayed text lowercase ✔️, without prefix ✔️
• copied data lowercase ✔️, with prefix ❌

on-chain -> receive (SegWit/Taproot)

• QR data uppercase ✔️, with prefix ✔️
• displayed text uppercase ❌, with prefix ❌
• copied data lowercase ✔️, without prefix ✔️

on-chain -> receive (Nested SegWit)

• QR data mixed case ✔️, with prefix ✔️
• displayed text mixed case ✔️, with prefix ❌
• copied data mixed case ✔️, without prefix ✔️

on-chain -> receive (legacy)
Not tested (possible via accounts?)