code: func NewDNSProviderConfig(config *Config) (*DNSProvider, error) {
  	if config == nil {
  		return nil, errors.New("glesys: the configuration of the DNS provider is nil")
  	}
  
  	if config.APIUser == "" || config.APIKey == "" {
  		return nil, fmt.Errorf("glesys: incomplete credentials provided")
  	}
  
  	if config.TTL < minTTL {
  		return nil, fmt.Errorf("glesys: invalid TTL, TTL (%d) must be greater than %d", config.TTL, minTTL)
  	}
  
  	return &DNSProvider{
  		config:        config,
  		activeRecords: make(map[string]int),
  	}, nil
  }
docs: // NewDNSProviderConfig return a DNSProvider instance configured for GleSYS.