pack_uuid_namespace

# File activesupport/lib/active_support/core_ext/digest/uuid.rb, line 58
    def self.pack_uuid_namespace(namespace)
      if [DNS_NAMESPACE, OID_NAMESPACE, URL_NAMESPACE, X500_NAMESPACE].include?(namespace)
        namespace
      elsif use_rfc4122_namespaced_uuids == true
        match_data = namespace.match(/\A(\h{8})-(\h{4})-(\h{4})-(\h{4})-(\h{4})(\h{8})\z/)

        raise ArgumentError, "Only UUIDs are valid namespace identifiers" unless match_data.present?

        match_data.captures.map { |s| s.to_i(16) }.pack("NnnnnN")
      else
        ActiveSupport::Deprecation.warn <<~WARNING.squish
          Providing a namespace ID that is not one of the constants defined on Digest::UUID generates an incorrect UUID value according to RFC 4122.
          To enable the correct behavior, set the Rails.application.config.active_support.use_rfc4122_namespaced_uuids configuration option to true.
        WARNING

        namespace
      end
    end