/**
  * @return JSON with reagents list which expiration date is closer than one week.
  */
 public function getCloseToExpirationDate()
 {
     $date = new \DateTime();
     $date->add(new \DateInterval('P7D'));
     $date = $date->format('Y-m-d');
     $odczynniki = Odczynnik::where('data_waznosci', '<=', $date)->get();
     return response()->json($odczynniki);
 }