code: func (s *RegistrarService) EnableDomainAutoRenewal(accountID string, domainName string) (*domainResponse, error) {
  	path := versioned(fmt.Sprintf("/%v/registrar/domains/%v/auto_renewal", accountID, domainName))
  	domainResponse := &domainResponse{}
  
  	resp, err := s.client.put(path, nil, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	domainResponse.HttpResponse = resp
  	return domainResponse, nil
  }
docs: // EnableDomainAutoRenewal enables auto-renewal for the domain.
  //
  // See https://developer.dnsimple.com/v2/registrar/auto-renewal/#enable