Add OWNER_DERIV_PATH for MAB trusted names

[apaillier-ledger]

Description

Yet another spec update, follow-up to #942.

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 51.60%. Comparing base (40d5d8a) to head (8b3c96b).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #956   +/-   ##
========================================
  Coverage    51.60%   51.60%           
========================================
  Files           17       17           
  Lines         1773     1773           
  Branches       215      215           
========================================
  Hits           915      915           
  Misses         849      849           
  Partials         9        9           

Flag	Coverage Δ
unittests	51.60% <ø> (ø)

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