TypeScript (Node): Better support for binary upload and download

Created by: clemens-smartparking

Is your feature request related to a problem? Please describe.

When having a form data parameter, e.g.:

{
    "name": "file",
    "required": true,
    "in": "formData",
    "description": "",
    "type": "file"
}

the generated API simply takes a Buffer object. However, I think it would be nice to support the other request options, especially the one to pass meta data along with the file (also see the example on https://github.com/request/request in the 'multipart/form-data (Multipart Form Uploads)' section).

When downloading a file the generated API seems to ignores the produces swagger spec, e.g. when using:

"produces": [
    "application/octet-stream"
],

the request is done with application/json (or am I doing something wrong?)

Describe the solution you'd like

This is how I currently do the file upload and download:

  const part = {
        value: Buffer.from('Test file content'),
        options: {
            filename: 'filename'
        }
  }
  const putResponse = await api.filePut(part as any);

  const getResponse = await api.filesGet(putResponse.body.uri,
    {
      headers: {
        Accept: 'application/octet-stream'
      }
    });

There are two hacks here:

the part object is cast to any because the api expect a Buffer (it works anyway)
the Accept: 'application/octet-stream' header must be passed in manually