$client = new GuzzleHttp\Client([
  'base_uri' => 'https://badgekit.example.com'
]);
$middleware = new Caxy\BadgeKit\JwtMiddleware('MASTER_SECRET_FROM_BADGEKIT');

$stack = $client->getConfig('handler');
$stack->push(GuzzleHttp\Middleware::mapRequest($middleware));

$serviceClient = new Caxy\BadgeKit\ServiceClient($client);
$command = $serviceClient->getCommand('get_reviews', [
  'system' => 'example',
  'application' => '235f684c5e5f88f1575434403adc2562',
  'badge' => 'a-groovy-badge',
]);
$result = $serviceClient->execute($command);