I need to post multipart data, however I have to set the custom header for that. I read the [httpclient module](https://nim-lang.org/docs/httpclient.html), I usually use `postContent` when multipart-data or `request` when sending JSON.
I think I need to use `request` but I have no idea the format for body/payload I need to send, so could anyone give advice how to do that? Thanks in advance
