code: func (u *UserV1) Check() error {
  	if u.Name == "" {
  		return trace.BadParameter("user name cannot be empty")
  	}
  	for _, login := range u.AllowedLogins {
  		_, _, err := parse.IsRoleVariable(login)
  		if err == nil {
  			return trace.BadParameter("role variables not allowed in allowed logins")
  		}
  	}
  	for _, id := range u.OIDCIdentities {
  		if err := id.Check(); err != nil {
  			return trace.Wrap(err)
  		}
  	}
  	return nil
  }
docs: // Check checks validity of all parameters