docs: @FromString
      public static CurrencyUnit of(String currencyCode) {
          MoneyUtils.checkNotNull(currencyCode, "Currency code must not be null");
          CurrencyUnit currency = currenciesByCode.get(currencyCode);
          if (currency == null) {
              throw new IllegalCurrencyException("Unknown currency '" + currencyCode + '\'');
          }
          return currency;
      }