docs: public BigMoney minusRetainScale(double amountToSubtract, RoundingMode roundingMode) {
          if (amountToSubtract == 0) {
              return this;
          }
          BigDecimal newAmount = amount.subtract(BigDecimal.valueOf(amountToSubtract));
          newAmount = newAmount.setScale(getScale(), roundingMode);
          return BigMoney.of(currency, newAmount);
      }