possible cj extension to support uploads. if "file" property appears in the "template" object then client SHOULD use multipart/form-data for sending the request body.

attach-template.js

// cj write template
{
  "template" : {
    "data" : [
      {"name" : "qwe", "value" : ""},
      {"name" : "rty", "file" : ""}
    ]
  }
}

upload-request.txt

Content-type: multipart/form-data, boundary=AaB03x

--AaB03x
content-disposition: form-data; name="document"
Content-Type: application/vnd.collection+json
{ "template": {
  "data": [
    { "name": "qwe", "value": "my picture" }
  ]
}

--AaB03x
Content-disposition: attachment; name="rty"; filename="portrait.tiff"
Content-type: image/tiff
Content-Transfer-Encoding: binary

  ...contents...
--AaB03x--