Implement readiness endpoint (/api/ready) that returns:
- {"ready":true} (HTTP 200) during normal operation
- {"ready":false} (HTTP 503) during graceful shutdown
Key changes:
- Added readiness context to control readiness state
- Modified server.NewServer() to accept readiness context
- Implemented handleReadiness() with context-aware logic
- Updated cmd/server/main.go to manage readiness state
- Readiness set to false when shutdown signal received
- Updated test script to validate readiness behavior
- Added comprehensive documentation for readiness endpoint
This allows Kubernetes/service meshes to stop routing traffic
to the pod during graceful shutdown while allowing existing
requests to complete. Health endpoint continues to return
happy status during shutdown for proper orchestration.