code: func (a *TestAuthServer) Trust(remote *TestAuthServer, roleMap services.RoleMap) error {
  	remoteCA, err := remote.AuthServer.GetCertAuthority(services.CertAuthID{
  		Type:       services.HostCA,
  		DomainName: remote.ClusterName,
  	}, false)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	err = a.AuthServer.UpsertCertAuthority(remoteCA)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	remoteCA, err = remote.AuthServer.GetCertAuthority(services.CertAuthID{
  		Type:       services.UserCA,
  		DomainName: remote.ClusterName,
  	}, false)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	remoteCA.SetRoleMap(roleMap)
  	err = a.AuthServer.UpsertCertAuthority(remoteCA)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	return nil
  }
docs: // Trust adds other server host certificate authority as trusted