Default path builder to server auth

[djc]

As suggested in

• Expose builder-like interface for path verification #486

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.01%. Comparing base (0fe5e6c) to head (5b16fa7).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #493   +/-   ##
=======================================
  Coverage   97.01%   97.01%           
=======================================
  Files          20       20           
  Lines        3950     3950           
=======================================
  Hits         3832     3832           
  Misses        118      118           

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[briansmith]

This would make it to easy to accidentally verify a client auth certificate (or an OCSP signer or similar) with the wrong EKU, IMO.

[ctz]

I think the current requirement to provide a ExtendedKeyUsageValidator up-front is preferable, really.