docs: public static ExchangeRateProvider getExchangeRateProvider(String... providers){
          if(providers.length == 0){
              List<String> defaultProviderChain = getDefaultConversionProviderChain();
              return getMonetaryConversionsSpi().getExchangeRateProvider(ConversionQueryBuilder.of().setProviderNames(
                      defaultProviderChain.toArray(new String[defaultProviderChain.size()])).build());
          }
          ExchangeRateProvider provider = getMonetaryConversionsSpi()
                  .getExchangeRateProvider(ConversionQueryBuilder.of().setProviderNames(providers).build());
          return Optional.ofNullable(provider)
                  .orElseThrow(() -> new MonetaryException("No such rate provider: " + Arrays.toString(providers)));
      }