@ResponseBody
public UploadFilePathResponse composeExperimentAttachmentDestination(@PathVariable("id") long attachmentId, Principal principal) {
final long userId = getUserId(principal);
//TBD: should we verify attachment exists?
final NodePath nodePath = storedObjectPaths.experimentAttachmentPath(userId, attachmentId);
return new UploadFilePathResponse(nodePath.getPath());
}