Using API to create comment attachment with existing URL instead of upload token.

Hello.

I'm writing an APP using the ZAFClient api that creates a new comment.  The new comment will add a CC and include the attachment from the original ticket description.

The /api/v2/tickets/ interface where the comment uploads takes a token returned from api/v2/uploads.  But, in my case, the attachment is already part of the ticket.  I would like to refer to the original contentUrl in the new comment for 2 reasons - (1) I would like to not duplicate the storage usage for the tickets and (2) avoid the complication of downloading then uploading the file.

Is there a way to specify the contentUrl during the comment creation?  Or maybe a better way to add this to the zendesk page?

Thanks,