docs: def post(self, *args, **kwargs):
          """Save file and return saved info or report errors."""
          if self.upload_allowed():
              form = self.get_upload_form()
              result = {}
              if form.is_valid():
                  storage = self.get_storage()
                  result['is_valid'] = True
                  info = form.stash(storage, self.request.path)
                  result.update(info)
              else:
                  result.update({
                      'is_valid': False,
                      'errors': form.errors,
                  })
              return HttpResponse(json.dumps(result), content_type='application/json')
          else:
              return HttpResponseForbidden()