chore: Participant self method as protected

[wolf4ood]

What this PR changes/adds

Changes Participant#self method to protected for extensibility

Why it does that

extensibility

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.05%. Comparing base (7f20ba5) to head (50564ef).
Report is 159 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4036      +/-   ##
==========================================
+ Coverage   71.74%   74.05%   +2.31%     
==========================================
  Files         919      988      +69     
  Lines       18457    20053    +1596     
  Branches     1037     1126      +89     
==========================================
+ Hits        13242    14851    +1609     
+ Misses       4756     4720      -36     
- Partials      459      482      +23     

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