Post API Documents with files from external source

[tanya]

Hello

http://forum.espocrm.com/forum/developer-help/25990-espocrm-api-attachment-empty-response

As I know, the first method works too

[yuri]

Framework allowing implementations for external sources will be added with 4.5.0 release.

[rgcadavos]

I'm using Postman (Chrome App Extension) for sending REST API requests. How can we send post request for Document with files?
Should we upload it first to http://<espocrm_baseurl>/api/v1/Attachment/action/upload ?

Thanks.