Add HTTP PQC Example for Java 21

[JiriOndrusek]

Fixes apache/camel-quarkus#8648

Adds a new Camel Quarkus example demonstrating native Post-Quantum Cryptography (PQC) support in TLS on Java 21 using BouncyCastle JSSE provider.

Summary

This example demonstrates the recommended approach for PQC on Java 21+, which is significantly simpler than the Java 17 workaround (http-pqc-j17).

Key Features

• TLS 1.3 with X25519MLKEM768 hybrid cipher suite combining classical X25519 with quantum-resistant ML-KEM-768
• BouncyCastle JSSE provider (bctls-jdk18on) for native PQC support
• Standard Quarkus SSL configuration - no custom trust managers or manual signature validation needed
• Auto-generated self-signed certificates for development and testing
• Comprehensive documentation comparing Java 17 vs Java 21 approaches

Comparison with Java 17 Example

Aspect	Java 17 (http-pqc-j17)	Java 21 (http-pqc-j21)
PQC Location	Application-level validation via custom X509TrustManager	Native TLS 1.3 protocol support
Certificate Type	Hybrid Chimera certificates (RSA + ML-DSA-65)	Standard X.509 certificates
Cipher Suite	Standard TLS, PQC validated separately	TLS_X25519MLKEM768 hybrid key exchange
Complexity	High - custom certificate generation, manual signature validation (2314 lines)	Low - standard Quarkus SSL configuration (622 lines)
Production Ready	Workaround for Java 17 limitations	Recommended approach for Java 21+

Implementation Details

1. Security Provider: Registers BouncyCastle JSSE as primary provider on startup
2. Certificate Generation: Auto-generates RSA-2048 keypairs and self-signed certificates
3. TLS Configuration: Standard Quarkus SSL properties with mTLS enabled
4. Hybrid Key Exchange: X25519 + ML-KEM-768 provides both classical and quantum resistance

Test Plan

• ✅ Unit tests verify certificate generation and PQC endpoints
• ✅ Integration test (HttpPqcIT) runs in native mode
• ✅ All tests passing in JVM and native modes

Documentation

The example includes:

• Comprehensive README with architecture diagrams
• Comparison table showing differences from Java 17 approach
• Migration guide from Java 17 to Java 21
• References to NIST standards and IETF drafts

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