test(protocol): add comprehensive protocol conformance test

[lichexb]

Description

Restructure OAuth DCR and OAuth client authentication process to make framework standard-compliant, and add comprehensive protocol conformance & cross-protocol interoperability tests.

This PR includes three main areas of work:

1. DCR restructuring: Make agent use DCR client assertion to execute PAR and token exchange
2. Client authentication refactoring: Standardize OAuth2 client authentication across the framework
3. Protocol conformance testing: Add 9 conformance test suites and cross-protocol interoperability tests

Fixes #(issue)

Type of Change

• New feature
• Code refactoring
• Test additions or updates
• Documentation update
• Bug fix
• Breaking change
• Performance improvement
• Other (please describe)

Changes Made

List the key changes made in this PR:

• Core Module: Restructured ClientAssertionAuthentication and ClientAssertionGenerator, added unified OAuth2ClientAuthentication abstraction, removed ParClientAuthentication and InMemoryOAuth2DcrClientStore
• Framework Module: Refactored DefaultAgent orchestration to use DCR client assertion for PAR and token exchange, removed ParRequest model
• Spring Boot Starter: Enhanced OAuth2ClientAuthenticator with comprehensive authentication method support, updated controllers and auto-configurations
• Integration Tests: Added 9 protocol conformance test suites (OIDC Discovery, Token Endpoint, PAR, DCR, JWKS, ID Token, WIMSE WIT/WPT, Token Exchange) and ProtocolInteroperabilityConformanceTest with 18 cross-protocol test cases
• Documentation: Added 09-wimse-dcr-integration.md architecture documentation
• Scripts: Added run-conformance-tests.sh and diagnose-conformance-env.sh for automated conformance testing

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing completed
• All existing tests pass

Test Instructions:

# Run unit tests
mvn test

# Run protocol conformance tests (requires sample services running)
cd open-agent-auth-integration-tests
./scripts/run-conformance-tests.sh

# Run specific conformance test
./scripts/run-conformance-tests.sh --test-class ProtocolInteroperabilityConformanceTest

Checklist

• Code follows coding standards
• Self-review performed
• Documentation updated
• No new warnings
• Tests added/updated
• All tests pass locally
• CHANGELOG.md updated

Breaking Changes

If this PR introduces breaking changes, please describe them here:

• Description: ParClientAuthentication removed (replaced by unified OAuth2ClientAuthentication), InMemoryOAuth2DcrClientStore removed (consolidated into InMemoryOAuth2ClientStore), ParRequest model removed (PAR requests now use standard OAuth2 client authentication flow)
• Migration Path: Use ClientAssertionAuthentication or BasicAuthAuthentication instead of ParClientAuthentication

Additional Context

Add any other context, screenshots, or information about the PR here.

Protocols validated by conformance tests:

• OAuth 2.0 Token Endpoint (RFC 6749 §5)
• OAuth 2.0 Token Exchange (RFC 8693)
• OAuth 2.0 DCR (RFC 7591)
• OAuth 2.0 PAR (RFC 9126)
• OIDC Discovery (OpenID Connect Discovery 1.0)
• OIDC ID Token (OpenID Connect Core 1.0 §2)
• JWKS Endpoint (RFC 7517)
• WIMSE WIT/WPT (draft-ietf-wimse-workload-creds)
• Cross-Protocol Interoperability (DCR→PAR→Token, OIDC→JWKS, WIT→TokenExchange)

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Code Coverage Report

Overall Project	85.13%	🍏

There is no coverage information present for the Files changed

[fudaiyf]

LGTM