feat: Validate claims in initiate-issuance of pre-auth flow

[bstasyszyn]

Claims are validated against a JSON schema (if provided) during the initiate-issuance step of the pre-auth flow. The request is immediately rejected if the claims fail to validate.

[codecov]

Codecov Report

Patch coverage: 87.50% and no project coverage change.

Comparison is base (232ab83) 85.34% compared to head (a95de6d) 85.34%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1433   +/-   ##
=======================================
  Coverage   85.34%   85.34%           
=======================================
  Files         164      164           
  Lines       10323    10338   +15     
=======================================
+ Hits         8810     8823   +13     
- Misses       1106     1107    +1     
- Partials      407      408    +1     

Files Changed	Coverage Δ
pkg/doc/validator/jsonschema/jsonschema.go	92.98% <ø> (ø)
...rvice/oidc4ci/oidc4ci_service_initiate_issuance.go	92.56% <81.81%> (-0.52%)	⬇️
cmd/vc-rest/startcmd/start.go	80.93% <100.00%> (+0.07%)	⬆️
pkg/restapi/v1/issuer/controller.go	92.12% <100.00%> (ø)
pkg/service/oidc4ci/oidc4ci_service.go	94.69% <100.00%> (+0.01%)	⬆️

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