@RequestMapping(value = "/{id}/control-letters", method = RequestMethod.GET)
  public String showControlLetters(
      @PathVariable("id") int id, Model model, final RedirectAttributes redirectAttributes) {
    if (!ticketsInvoiceService.invoiceExists(id)) throw new ResourceNotFoundException();

    List<ControlLetter> controlLetters = controlLetterService.findAll(id);
    handleFlashMessages(redirectAttributes, model);

    model.addAttribute("ticketsInvoiceId", id);
    model.addAttribute("controlLetters", controlLetters);

    return "controlLetter/find";
  }
  @RequestMapping(value = "/{invoiceId}/control-letters/{id}")
  public String showControlLetter(
      @PathVariable("invoiceId") int invoiceId, @PathVariable("id") int id, Model model) {

    ControlLetter controlLetter = controlLetterService.find(id);
    if (controlLetter == null) throw new ResourceNotFoundException();
    controlLetter.setIncomeId(invoiceId);

    List<Employee> employees = employeeService.findAll(Employee.EmployeePosition.CASIER.getId());

    model.addAttribute("employees", employees);
    model.addAttribute("controlLetter", controlLetter);
    return "controlLetter/edit";
  }