title: Recurly custom invoice fields
body: <p>Is it possible to add a custom field to Recurly Invoice or customize generated invoice in general?</p>
  
  <p>For example, one would like to add a Reference text-field. So when the user checks out the order, he can insert Reference name and then it would be displayed at the generated invoice near billing details (company name, address).</p>
  
  <p>Looks like Recurly API doesn't have tools for such customization, but still may be something was missed.</p>