Export attachment urls

Hello,

thank you for the really useful project! However, I noticed that translation-server does not export all data available to zotero in the /web endpoint. The filtered item-fields can be found here:

translation-server/src/utilities.js

Line 68 in 6045c70

if(field === "complete" || field === "itemID" || field === "attachments"

I'm specifically missing the attachment field. The attached patch (include-attachments.patch.txt, modeled similar to the handling of notes as explicit items) will export the data, for instance:

$ ./translate_url 'http://drops.dagstuhl.de/opus/frontdoor.php?source_opus=10246'
[{
  "key": "P5KKCZHW",
  "version": 0,
  "itemType": "conferencePaper",
  "creators": [
   {
    "firstName": "Spyros",
    "lastName": "Angelopoulos",
    "creatorType": "author"
   },
   ...
  ],
  "tags": [...],
  "title": "Best-Of-Two-Worlds Analysis of Online Search",
  ...,
  "accessDate": "2019-03-13T09:46:39Z"
 },
 {
  "itemType": "attachment",
  "parentItem": "P5KKCZHW",
  "title": "Snapshot",
  "mimeType": "text\/html",
  "url": "http:\/\/drops.dagstuhl.de\/opus\/frontdoor.php?source_opus=10246"
 },
 {
  "itemType": "attachment",
  "parentItem": "P5KKCZHW",
  "title": "Full Text PDF",
  "mimeType": "application\/pdf",
  "url": "http:\/\/drops.dagstuhl.de\/opus\/volltexte\/2019\/10246\/pdf\/LIPIcs-STACS-2019-7.pdf"
}]

So I wonder whether this was a conscious decision to remove attachments (especially those kinds that simply carry an url field) or whether those could be included into the output. Please note that I'm not really familiar with the codebase or javascript, so the patch might do quite stupid things :D

Thank you for your work and consideration.

Any updates on this issue?