code: func (a *AuthServer) activateCertAuthority(t services.TrustedCluster) error {
  	err := a.ActivateCertAuthority(services.CertAuthID{Type: services.UserCA, DomainName: t.GetName()})
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	return trace.Wrap(a.ActivateCertAuthority(services.CertAuthID{Type: services.HostCA, DomainName: t.GetName()}))
  }
docs: // activateCertAuthority will activate both the user and host certificate
  // authority given in the services.TrustedCluster resource.