NBGL cherry-pick for API level 21

[apaillier-ledger]

Description

#787

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.76%. Comparing base (603cf09) to head (c3524ee).
Report is 72 commits behind head on API_LEVEL_21.

Additional details and impacted files

@@                Coverage Diff                @@
##           API_LEVEL_21     #788       +/-   ##
=================================================
- Coverage         60.19%   35.76%   -24.44%     
=================================================
  Files                12       13        +1     
  Lines              1726     1591      -135     
=================================================
- Hits               1039      569      -470     
- Misses              687     1022      +335     

Flag	Coverage Δ
unittests	35.76% <ø> (-24.44%)	⬇️

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