Properly upgrade jsonschema library from v5 to v6

[JAORMX]

Summary

This PR properly handles the major version upgrade of the github.com/santhosh-tekuri/jsonschema library from v5 to v6.

In Go, major version upgrades (v2+) require updating the import path to include the new version suffix. PR #2158 attempted this upgrade but only updated go.mod without updating the import paths and adapting to API changes, which caused compilation failures.

Changes

• go.mod: Removed v5 dependency, kept only v6 with proper import path
• pkg/registry/schema_validation.go:
  • Updated import path from jsonschema/v5 to jsonschema/v6
  • Adapted to v6 API: AddResource() now accepts parsed JSON (any) instead of io.Reader
  • Updated error handling to use v6's BasicOutput() and OutputError.String() methods
• pkg/registry/schema_validation_test.go: Adjusted test expectation for v6's error message format ("additional properties" instead of "additionalProperties")

Testing

All tests pass successfully:

• Unit tests: go test ./pkg/registry/... ✅
• Full test suite: task test ✅

Migration Notes from v5 to v6

Key API changes in jsonschema v6:

1. AddResource() signature changed from (url string, reader io.Reader) to (url string, doc any)
2. ValidationError structure changed - uses ErrorKind and BasicOutput() instead of Message field
3. Error message formatting is slightly different but still clear and helpful

See upstream migration discussion: santhosh-tekuri/jsonschema#172

Closes #2158

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.13%. Comparing base (47e5fd8) to head (b898343).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/registry/schema_validation.go	60.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2168      +/-   ##
==========================================
- Coverage   53.16%   53.13%   -0.03%     
==========================================
  Files         222      222              
  Lines       28904    28908       +4     
==========================================
- Hits        15366    15361       -5     
- Misses      12397    12403       +6     
- Partials     1141     1144       +3     

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[jhrozek]

patch LGTM, but conflict needs to be resolved

[JAORMX]

@jhrozek resolved