code: func (r *RotateRequest) Types() []services.CertAuthType {
  	switch r.Type {
  	case "":
  		return []services.CertAuthType{services.HostCA, services.UserCA}
  	case services.HostCA:
  		return []services.CertAuthType{services.HostCA}
  	case services.UserCA:
  		return []services.CertAuthType{services.UserCA}
  	}
  	return nil
  }
docs: // Types returns cert authority types requested to be rotated.