code: func (p DummyPlugin) Validate(endpoint plugin.ShieldEndpoint) error {
  	var (
  		s    string
  		err  error
  		fail bool
  	)
  
  	s, err = endpoint.StringValue("data")
  	if err != nil {
  		fmt.Printf("@R{\u2717 data   %s}\n", err)
  		fail = true
  	} else {
  		fmt.Printf("@G{\u2713 data}  @C{%s}\n", s)
  	}
  
  	if fail {
  		return fmt.Errorf("dummy: invalid configuration")
  	}
  	return nil
  }
docs: // Called to validate endpoints from the command line