test(oidc): add comprehensive PKCE test coverage with improved diagnostics (PROJQUAY-9281)
Add extensive test suite for PKCE (Proof Key for Code Exchange) functionality
across multiple layers of the application:
Test Coverage:
- Core PKCE utilities (code_verifier generation, S256 challenge computation)
- OAuth base class integration with PKCE parameters
- OIDC service with PKCE fixtures and authorization scenarios
- Dedicated PKCE flow testing (S256/plain methods, public client support)
- API endpoint integration for user PKCE operations
- Login flow integration with session-based verifier storage
Features Tested:
- S256 and plain code challenge methods
- Public client support (omitting client_secret)
- Session-based code_verifier storage and retrieval
- Error handling for missing/invalid verifiers
- Integration with existing OIDC authorization flows
- Descriptive assertion messages for CI diagnostics
All tests include informative error messages with expected vs actual values
to improve debugging in CI environments.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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