code: private function getCurrencyId($currency)
      {
          /**
           * @var EntityRepository $currencyRepository
           */
          $currencyRepository = Shopware()->Models()->getRepository(CurrencyModel::class);
  
          /**
           * @var null|CurrencyModel $model
           */
          $model = $currencyRepository->findOneBy(['currency' => $currency]);
  
          if (null === $model) {
              throw new InvalidArgumentException('could not find currency model by currency: ' . $currency);
          }
  
          return $model->getId();
      }
docs: @param string $currency
  
  @return int