feat(cawg_identity): Implement identity assertion validation

[scouten-adobe]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 83.54430% with 13 lines in your changes missing coverage. Please review.

Project coverage is 79.08%. Comparing base (55ddca1) to head (ab74ecb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
..._identity/src/identity_assertion/signer_payload.rs	79.16%	10 Missing ⚠️
cawg_identity/src/identity_assertion/assertion.rs	90.32%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #843      +/-   ##
==========================================
+ Coverage   79.04%   79.08%   +0.03%     
==========================================
  Files         122      123       +1     
  Lines       31379    31458      +79     
==========================================
+ Hits        24804    24879      +75     
- Misses       6575     6579       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.