test: add comprehensive tests for protocol version propagation and resourceMetadataUrl functionality

This commit adds 21 new comprehensive test cases to verify the OAuth authentication
enhancements from commit bb23147, covering:

1. Protocol Version Propagation Tests:
   - Custom protocol version headers in protected resource metadata discovery
   - Custom protocol version headers in OAuth metadata discovery
   - Default protocol version usage when not specified
   - CORS fallback behavior with protocol versions
   - Protocol version propagation through full auth flow

2. Custom Resource Metadata URL Tests:
   - Custom URL routing instead of default well-known locations
   - Custom URLs combined with protocol version headers
   - Various URL format handling (ports, query params, fragments, localhost)
   - CORS fallback with custom URLs

3. Integration Tests:
   - Resource validation working correctly with new parameters
   - Fallback behavior when metadata fails
   - Token exchange flow with protocol version propagation
   - Token refresh flow with protocol version propagation
   - All parameters working together in complex scenarios

4. Edge Case Tests:
   - Edge case protocol versions (old dates, future dates, suffixes, empty strings)
   - Various custom URL formats (ports, query params, fragments, localhost)
   - Combined CORS fallback scenarios

All tests maintain compatibility with existing functionality and ensure no regressions.
Fixed duplicate variable declaration issue in auth.ts discovered during testing.

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Co-Authored-By: Claude <[email protected]>

Author: ochafik