code: func (c *Client) DomainList(appIdentity string, lr *ListRange) ([]Domain, error) {
  	req, err := c.NewRequest("GET", "/apps/"+appIdentity+"/domains", nil, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	if lr != nil {
  		lr.SetHeader(req)
  	}
  
  	var domainsRes []Domain
  	return domainsRes, c.DoReq(req, &domainsRes)
  }
docs: // List existing domains.
  //
  // appIdentity is the unique identifier of the Domain's App. lr is an optional
  // ListRange that sets the Range options for the paginated list of results.