private function validateDefaultAuthorSetting($name, $value)
    {
        $definedValues = [
            self::DEFAULT_VALUE_EMPTY,
            self::DEFAULT_CURRENT_USER,
        ];

        if (!in_array($value, $definedValues, true)) {
            return new ValidationError(
                "Setting '%setting%' has unknown default value",
                null,
                [
                    '%setting%' => $name,
                ],
                "[$name]"
            );
        }

        return null;
    }