Add preliminary VC support

[scouten-adobe]

EARLY DRAFT: Add support for verifiable credentials in CAWG identity assertion

[codecov]

Codecov Report

Attention: Patch coverage is 65.12262% with 128 lines in your changes missing coverage. Please review.

Project coverage is 76.67%. Comparing base (94d5b12) to head (2568ac5).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/w3c_vc/temp_cose.rs	37.14%	66 Missing ⚠️
src/w3c_vc/identity_assertion_vc.rs	38.46%	16 Missing ⚠️
src/identity_assertion/signer_payload.rs	73.21%	15 Missing ⚠️
src/identity_assertion/named_actor.rs	0.00%	12 Missing ⚠️
src/w3c_vc/cose_vc_signature_handler.rs	94.03%	9 Missing ⚠️
src/internal/naive_credential_handler.rs	0.00%	6 Missing ⚠️
src/identity_assertion/mod.rs	70.00%	3 Missing ⚠️
src/identity_assertion/validation_error.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #26       +/-   ##
===========================================
- Coverage   87.32%   76.67%   -10.66%     
===========================================
  Files           9       15        +6     
  Lines         363      673      +310     
===========================================
+ Hits          317      516      +199     
- Misses         46      157      +111     

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