$app->post('/guests/', function () use($app) {
    $guestJson = $app->request()->getBody();
    $newGuest = json_decode($guestJson, true);
    if ($newGuest) {
        $guest = GuestService::add($newGuest);
        echo "Guest {$guest['name']} added on database";
    } else {
        $app->response->setStatus(400);
        echo "Invalid JSON";
    }
});
$app->put('/guests/', function () use($app) {
    $guestJson = $app->request()->getBody();
    $updatedGuest = json_decode($guestJson, true);
    if ($updatedGuest && $updatedGuest['id']) {
        if (GuestService::update($updatedGuest)) {
            echo "Guest {$updatedGuest['name']} updated on database";
        } else {
            $app->response->setStatus('404');
            echo "Guest not found";
        }
    } else {
        $app->response->setStatus(400);
        echo "Invalid JSON";
    }
});
/*
HTTP DELETE /api/guests/:id
RESPONSE 200 OK 
{
  "status": "true",