feat(cert): add registry-based DNS provider system with 21 libdns providers

Refs #37

internal/service/service.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/cedar2025/xboard-node/internal/cert"
+	"github.com/cedar2025/xboard-node/internal/cert/dnsproviders"
 	"github.com/cedar2025/xboard-node/internal/config"
 	"github.com/cedar2025/xboard-node/internal/controlplane"
 	"github.com/cedar2025/xboard-node/internal/kernel"
@@ -1219,15 +1220,14 @@ func validateRuntimeCertConfig(spec *model.NodeSpec) error {
 	if mode != "dns" {
 		return nil
 	}
-	provider := strings.ToLower(strings.TrimSpace(spec.CertConfig.DNSProvider))
-	switch provider {
-	case "cloudflare", "cf", "alidns", "aliyun":
-		return nil
-	case "":
+	provider := strings.TrimSpace(spec.CertConfig.DNSProvider)
+	if provider == "" {
 		return fmt.Errorf("dns cert mode requires cert_config.dns_provider")
-	default:
-		return fmt.Errorf("unsupported cert_config.dns_provider %q (supported: cloudflare, alidns)", spec.CertConfig.DNSProvider)
 	}
+	if _, ok := dnsproviders.Get(provider); !ok {
+		return fmt.Errorf("unsupported cert_config.dns_provider %q (supported: %s)", provider, strings.Join(dnsproviders.CanonicalNames(), ", "))
+	}
+	return nil
 }
 
 func validateRealityRequirements(spec *model.NodeSpec, _ string) error {

internal/service/service_test.go

@@ -3,6 +3,7 @@ package service
 import (
 	"context"
 	"errors"
+	"strings"
 	"testing"
 
 	"github.com/cedar2025/xboard-node/internal/cert"
@@ -214,7 +215,7 @@ func TestValidateNodeRuntimeRejectsUnsupportedDNSProvider(t *testing.T) {
 	if err.Error() == "" {
 		t.Fatal("expected non-empty error")
 	}
-	if got := err.Error(); got != "unsupported cert_config.dns_provider \"3123123\" (supported: cloudflare, alidns)" {
+	if got := err.Error(); !strings.HasPrefix(got, `unsupported cert_config.dns_provider "3123123" (supported: `) {
 		t.Fatalf("unexpected error: %v", got)
 	}
 }