code: func (s *CA) ActivateCertAuthority(id services.CertAuthID) error {
  	item, err := s.Get(context.TODO(), backend.Key(authoritiesPrefix, deactivatedPrefix, string(id.Type), id.DomainName))
  	if err != nil {
  		if trace.IsNotFound(err) {
  			return trace.BadParameter("can not activate cert authority %q which has not been deactivated", id.DomainName)
  		}
  		return trace.Wrap(err)
  	}
  
  	certAuthority, err := services.GetCertAuthorityMarshaler().UnmarshalCertAuthority(
  		item.Value, services.WithResourceID(item.ID), services.WithExpires(item.Expires))
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	err = s.UpsertCertAuthority(certAuthority)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	err = s.Delete(context.TODO(), backend.Key(authoritiesPrefix, deactivatedPrefix, string(id.Type), id.DomainName))
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	return nil
  }
docs: // ActivateCertAuthority moves a CertAuthority from the deactivated list to
  // the normal list.