chore: x-caddy extension type in compose

pkg/client/compose/caddy.go

@@ -0,0 +1,35 @@
+package compose
+
+import "fmt"
+
+const CaddyExtensionKey = "x-caddy"
+
+type Caddy struct {
+	Config string `yaml:"config" json:"config"`
+}
+
+// DecodeMapstructure decodes x-caddy extension from either a string or an object.
+// When x-caddy is a string, it's mapped directly to the Config field.
+func (c *Caddy) DecodeMapstructure(value any) error {
+	switch v := value.(type) {
+	case *Caddy:
+		// Already decoded, happens when mapstructure is called after initial parsing.
+		*c = *v
+		return nil
+	case string:
+		// Handle x-caddy: "caddyfile config"
+		*c = Caddy{Config: v}
+	case map[string]any:
+		// Handle the long syntax with a config key.
+		if config, ok := v["config"]; ok {
+			configStr, ok := config.(string)
+			if !ok {
+				return fmt.Errorf("x-caddy.config must be a string, got %T", config)
+			}
+			*c = Caddy{Config: configStr}
+		}
+	default:
+		return fmt.Errorf("invalid type %T for x-caddy extension: expected string or object", value)
+	}
+	return nil
+}