docs: def resend_invoices(modeladmin, request: HttpRequest, queryset: QuerySet):
      """
      Marks invoices with as un-sent.
      :param modeladmin:
      :param request:
      :param queryset:
      :return:
      """
      user = request.user
      assert isinstance(user, User)
      for obj in queryset:
          assert isinstance(obj, Invoice)
          admin_log([obj, user], 'Invoice id={invoice} marked for re-sending'.format(invoice=obj.id), who=user)
      queryset.update(sent=None)