Add HTTP health check endpoint for MinIO Sidekick

[Copilot]

Adds HTTP server responding with 200 OK on /health, /healthz, and / for MinIO Sidekick load balancer health monitoring.

Changes

• Health check server: Runs in background goroutine, starts on application launch
• CLI flag: --healthport (default: 8080) configures listener port
• Endpoints: All three paths return identical 200 OK responses

Implementation

// Added to main.go
func startHealthCheckServer(port string) {
    http.HandleFunc("/health", healthCheckHandler)
    http.HandleFunc("/healthz", healthCheckHandler)
    http.HandleFunc("/", healthCheckHandler)
    
    addr := ":" + port
    fmt.Printf("Starting health check server on %s\n", addr)
    if err := http.ListenAndServe(addr, nil); err != nil {
        fmt.Printf("Health check server error: %v\n", err)
    }
}

func healthCheckHandler(w http.ResponseWriter, r *http.Request) {
    w.WriteHeader(http.StatusOK)
    _, _ = w.Write([]byte("OK"))
}

// In main()
go startHealthCheckServer(*healthPort)

Non-invasive: health check runs independently of tape operations and S3 logic. Uses only Go standard library.

Original prompt

golang server that responds to minio sidekick health check with a 200

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