Add catalog-zone-gen tool

Generate RFC 9432 DNS catalog zone files from a declarative input file.
Parses zone-to-catalog assignments with optional group and coo properties,
produces deterministic BIND-format output with automatic SOA serial
management and change detection.

config.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+// CatalogConfig holds the configuration for a single catalog zone.
+type CatalogConfig struct {
+	Zone string `yaml:"zone"`
+}
+
+// SOAConfig holds the configurable SOA fields.
+type SOAConfig struct {
+	Mname string `yaml:"mname"`
+	Rname string `yaml:"rname"`
+}
+
+// Config holds the parsed catz.yaml configuration.
+type Config struct {
+	Catalogs map[string]CatalogConfig `yaml:"catalogs"`
+	SOA      SOAConfig                `yaml:"soa"`
+}
+
+func loadConfig(path string) (*Config, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("reading config: %w", err)
+	}
+
+	var cfg Config
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, fmt.Errorf("parsing config: %w", err)
+	}
+
+	if err := validateConfig(&cfg); err != nil {
+		return nil, err
+	}
+
+	// Normalize zone FQDNs
+	for name, cat := range cfg.Catalogs {
+		cat.Zone = normalizeFQDN(cat.Zone)
+		cfg.Catalogs[name] = cat
+	}
+	cfg.SOA.Mname = normalizeFQDN(cfg.SOA.Mname)
+	cfg.SOA.Rname = normalizeFQDN(cfg.SOA.Rname)
+
+	return &cfg, nil
+}
+
+func validateConfig(cfg *Config) error {
+	if len(cfg.Catalogs) == 0 {
+		return fmt.Errorf("config: no catalogs defined")
+	}
+	for name, cat := range cfg.Catalogs {
+		if cat.Zone == "" {
+			return fmt.Errorf("config: catalog %q has no zone defined", name)
+		}
+	}
+	if cfg.SOA.Mname == "" {
+		return fmt.Errorf("config: soa.mname is required")
+	}
+	if cfg.SOA.Rname == "" {
+		return fmt.Errorf("config: soa.rname is required")
+	}
+	return nil
+}
+
+func normalizeFQDN(name string) string {
+	name = strings.ToLower(strings.TrimSpace(name))
+	if name != "" && !strings.HasSuffix(name, ".") {
+		name += "."
+	}
+	return name
+}