public function postTambahUnit(Request $request)
 {
     $validator = Validator::make($request->all(), ['nama_unit' => 'required', 'singkatan' => 'required']);
     $request['created_by'] = Auth::user()->id;
     if ($validator->fails()) {
         return redirect()->back()->withErrors($validator)->withInput();
     }
     $input = $request->only(['nama_unit', 'singkatan', 'unit_atasan', 'created_by']);
     Unit::create($input);
     return redirect()->back();
 }