[FEATURE] Add performance/load testing and document capacity benchmarks

[cre8]

🚀 Feature Request

📝 Summary

Implement performance and load testing for EUDIPLO and document capacity benchmarks to help production planning and identify potential bottlenecks.

🎯 Problem Statement

Organizations evaluating EUDIPLO for production deployment need to understand its performance characteristics:

• Maximum transactions per second
• Response latency under load
• Resource consumption patterns
• Scalability limits

Currently, no performance testing or benchmark documentation exists.

💡 Proposed Solution

1. Add load testing scripts using k6 or Artillery
2. Test key scenarios:
   • Credential issuance (pre-auth and auth code flows)
   • Credential presentation (OID4VP)
   • Status list operations
   • API authentication throughput
3. Document results in a new performance guide
4. Add CI integration for performance regression testing

🔄 Alternatives Considered

• Manual testing: Not reproducible, no baselines
• Third-party benchmarks: Not specific to EUDIPLO use cases
• Production monitoring only: Reactive, not proactive planning

📋 Use Cases

• Production capacity planning
• Infrastructure sizing decisions
• Identifying performance bottlenecks before deployment
• Comparing performance across versions
• Validating performance after optimizations

🎨 Implementation Ideas

Load testing scripts (k6 example):

// scripts/load-test/issuance.js
import http from 'k6/http';
import { check } from 'k6';

export const options = {
  stages: [
    { duration: '1m', target: 50 },
    { duration: '3m', target: 100 },
    { duration: '1m', target: 0 },
  ],
};

export default function () {
  // Test credential issuance flow
}

Documentation structure:

docs/
  deployment/
    performance.md  # New file
      - Test methodology
      - Hardware specifications
      - Benchmark results
      - Tuning recommendations

Metrics to capture:

• Requests per second (RPS)
• P50, P95, P99 latency
• Error rate under load
• CPU/memory utilization
• Database connection pool usage

🌍 Environment

Testing should cover:

• SQLite (development baseline)
• PostgreSQL (production)
• Different key management backends (db, vault)
• Single instance vs. scaled deployment

📋 Additional Context

• Existing monitoring stack: monitor/ (Prometheus + Grafana)
• OIDF conformance tests exist but don't measure performance
• Consider integration with existing CI pipeline

✔️ Checklist

• I have searched for existing feature requests before creating this one
• I have provided a clear description of the feature
• I have explained the use cases for this feature
• This feature aligns with the project's goals and scope