Add details.rst for c-extension-no-member

[jacobtylerwalls]

Closes #5953

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.80%. Comparing base (67acc96) to head (92e970b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9933   +/-   ##
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  Coverage   95.80%   95.80%           
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  Files         174      174           
  Lines       18933    18933           
=======================================
  Hits        18139    18139           
  Misses        794      794           

[Pierre-Sassoulas]

Wow, this was the last bit of message documentation 🎉

[DanielNoord]

Perhaps we should now add an assertion that it should always be present?

[Pierre-Sassoulas]

Yeah working on it. I'm searching between the 100 existing branchs in my local repo. It's done in one if them. Currentely greping for keywords.. '^^