The documentation on the Ultimaker 3 (http://UM3/docs/api) contains good examples of how to do PUT and POST requests and I also found a good Python example by Daid) that handles the Digest authentication the Ultimaker 3 uses.
However, I can't find how to do the 'Digest' authentication from cURL. This is not in the examples in the documentation.
I tried adding "--digest --user id:key" to the command but it gives a "message": "400: Bad Request".
$ curl --digest --user 1269546bd8958aa0524c0