refactor: PR 1.4 migrate to jwx v3 and implement pure options for JWKS provider

[developerkunal]

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

🔧 Changes

This PR migrates JWT handling from go-jose v2 to lestrrat-go/jwx v3 and refactors JWKS provider to use pure options pattern.

JWT Library Migration

• Migrated from gopkg.in/go-jose/go-jose.v2 to github.com/lestrrat-go/jwx/v3
• Updated all JWT parsing, validation, and JWKS handling to use jwx v3 APIs
• Improved performance with jwx's native JWKS caching support

Pure Options Pattern for JWKS Provider

• Refactored jwks.NewProvider() and jwks.NewCachingProvider() to pure options pattern
• Changed all configuration to functional options (no positional parameters)
• Added comprehensive option validation with clear error messages

New Options API:

• WithIssuerURL(*url.URL) - required, sets the issuer URL for OIDC discovery
• WithCustomJWKSURI(*url.URL) - optional, bypasses discovery and uses custom JWKS endpoint
• WithCustomClient(*http.Client) - optional, uses custom HTTP client
• WithCacheTTL(time.Duration) - CachingProvider only, sets cache TTL (default: 15 minutes)
• WithCache(Cache) - CachingProvider only, uses custom cache implementation

Bug Fixes

• Fixed race condition in JWKS caching with proper lock synchronization
• Added URL validation to validator.WithIssuers for consistency with WithIssuer

Testing & Examples

• Improved test coverage: jwks 92.1%, validator 87.0%
• Added comprehensive tests for all 14 signature algorithms
• Updated http-example and http-jwks-example to use new API
• Documented pre-existing test failure in http-jwks-example with skip annotation

Breaking Changes

• jwks.NewProvider() and jwks.NewCachingProvider() now return (*Provider, error) instead of *Provider
• All provider configuration must use functional options

Migration Example:

// Before (v2)
provider := jwks.NewCachingProvider(issuerURL, 5*time.Minute)

// After (v3)
provider, err := jwks.NewCachingProvider(
    jwks.WithIssuerURL(issuerURL),
    jwks.WithCacheTTL(5*time.Minute),
)
if err != nil {
    log.Fatal(err)
}

📚 References

Part of v3 refactoring series:

• Builds on PR 1.3: validator pure options pattern
• Next: TBD

🔬 Testing

All tests pass with race detection:

go test ./validator -race -cover  # 87.0% coverage
go test ./jwks -race -cover       # 92.1% coverage
go test ./examples/http-example -v
go test ./examples/http-jwks-example -v

Manual Testing:

1. Run http-example: cd examples/http-example && go run main.go
2. Run http-jwks-example: cd examples/http-jwks-example && go run main.go
3. Both examples demonstrate new options API

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.46%. Comparing base (7cf5d00) to head (1da96e0).

Additional details and impacted files

@@                         Coverage Diff                         @@
##           v3-phase1-pr3-validator-options     #358      +/-   ##
===================================================================
+ Coverage                            97.95%   99.46%   +1.50%     
===================================================================
  Files                                   13       13              
  Lines                                  441      562     +121     
===================================================================
+ Hits                                   432      559     +127     
+ Misses                                   6        3       -3     
+ Partials                                 3        0       -3     

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