code: func (r RejectionReason) String() string {
  	switch r {
  	case Prohibited:
  		return "administratively prohibited"
  	case ConnectionFailed:
  		return "connect failed"
  	case UnknownChannelType:
  		return "unknown channel type"
  	case ResourceShortage:
  		return "resource shortage"
  	}
  	return fmt.Sprintf("unknown reason %d", int(r))
  }
docs: // String converts the rejection reason to human readable form.