Include IDP type and subject domain in configuration API response

[adityasaky]

Summary

This PR adds the IDP type and subject domain (for URI and Username IDPs) to the Fulcio configuration API response.

Release Note

Added IDP type and subject domain to Fulcio configuration API response

Documentation

None

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 8 lines in your changes missing coverage. Please review.

Project coverage is 50.33%. Comparing base (cf238ac) to head (6d5c0d6).
Report is 210 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/generated/protobuf/fulcio.pb.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1824      +/-   ##
==========================================
- Coverage   57.93%   50.33%   -7.61%     
==========================================
  Files          50       70      +20     
  Lines        3119     4198    +1079     
==========================================
+ Hits         1807     2113     +306     
- Misses       1154     1852     +698     
- Partials      158      233      +75     

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[haydentherapper]

Thank you!