how to upload files to laravel using restangular

I'm using restangular 1.51 with angular 1.6. My html looks like this

<input type="file" name="file" />

and the angular code (based on the discussion here):

let directive = {
  ..
  link: (scope, element, attrs) => {
        let inputElement = angular.element(element[0].querySelector('input'));
        inputElement.bind('change', function () {
        var formData = new FormData();
        formData.append('file', inputElement[0].files[0]);

        API.all('stores/csv').withHttpConfig({transformRequest: angular.identity})             .customPOST(formData,'' , undefined,
          { 'Content-Type': undefined }).then((response) => {console.log(response);
          });
    });

laravel code:

public function upload(Request $request)
{

    $this->validate($request, [
        'file' => 'required',
        'type'  => 'in:csv,xls,xlsx',
        ]);

    $file = $request->input('file');
    var_dump($file);
    return response()->success(['file' => $file]);
}

thing is the $file here is appearing as an empty array in the laravel dump. The documentation is pretty bad on this. Ideas?

via Chebli Mohamed