refactor(headers): use interfaces where possible

[susnux]

• final follow up on refactor: use interfaces where possible instead of instances #1417

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.93%. Comparing base (8b2be4f) to head (6a42fa9).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1484      +/-   ##
==========================================
- Coverage   86.14%   85.93%   -0.21%     
==========================================
  Files          30       29       -1     
  Lines         671      661      -10     
  Branches      195      193       -2     
==========================================
- Hits          578      568      -10     
  Misses         81       81              
  Partials       12       12              

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