code: func (u *Upstream) Validate() error {
  	if u.DestinationType != UpstreamDestTypeService &&
  		u.DestinationType != UpstreamDestTypePreparedQuery {
  		return fmt.Errorf("unknown upstream destination type")
  	}
  
  	if u.DestinationName == "" {
  		return fmt.Errorf("upstream destination name cannot be empty")
  	}
  
  	if u.LocalBindPort == 0 {
  		return fmt.Errorf("upstream local bind port cannot be zero")
  	}
  	return nil
  }
docs: // Validate sanity checks the struct is valid