code: func (n DeviceID) String() string {
  	if n == EmptyDeviceID {
  		return ""
  	}
  	id := base32.StdEncoding.EncodeToString(n[:])
  	id = strings.Trim(id, "=")
  	id, err := luhnify(id)
  	if err != nil {
  		// Should never happen
  		panic(err)
  	}
  	id = chunkify(id)
  	return id
  }
docs: // String returns the canonical string representation of the device ID