How do we implement a curl post in pharo

I have curl post to implement in pharo, but it seems like there is not much in term of explanation on how to do that. I saw few example but they ARE way simpler than what I need to. I would you do that inn pharos?

$ curl 'https://url_server' \
-X POST \
-H 'key: MY PASSWORD' \
-H 'Content-Type: application/json' \
-d \
'{
  "HEADER": "FOO",
  "DESK": "POO",
  "FORWARDTO": "another_url"
}'

I know that this is similar to post using Znclient like so:

 ZnClient new
    url: 'url_server';
    entity: (ZnEntity 
            with:'{"HEADER": "FOO", 
                   "DESK": "POO",
                   "FORWARDTO": "another_url"}'
            type: ZnMimeType applicationJson
            );
        post.

However where does the key goes to using this syntax?

Seems like you are looking for the way to set a HTTP header field for your request in Zinc?

Try ZnClient:

headerAt: key put: value
    "Set key equals value in the HTTP header of the current request"

Your code then could look like:

ZnClient new
    url: 'yourURL';
    headerAt: 'headerKey' put: 'headerValue'; 
    entity: (ZnEntity 
        with:'{"yourJSON": "Content"}'
        type: ZnMimeType applicationJson);
    post.

Zinc also has a nice feature, that shows you a curl command line invocation equivalent to the current request. So you can compare to the curl line you had in mind. Just print:

ZnClient new
    url: 'yourURL';
    headerAt: 'headerKey' put: 'headerValue'; 
    entity: (ZnEntity 
        with:'{"yourJSON": "Content"}'
        type: ZnMimeType applicationJson);
    method: #POST;
    curl.

You'll find a good documentation for using Zinc HTTP as client in the Enterprise Pharo book.