static <T> MultiConverter<T> wrapSingleInputConverter(final Function<String, List<T>> converter) {
            return values -> {
                if (NullSafe.isEmptyCollection(values)) {
                    return Collections.emptyList();
                } else {
                    // Call the converter for each
                    return values.stream()
                            .filter(val -> !NullSafe.isBlankString(val))
                            .flatMap(val -> converter.apply(val).stream())
                            .toList();
                }
            };
        }
Wraps a one to many function inside a {@link MultiConverter}. converter will be called once for each
value passed to {@link MultiConverter} so don't use this if converter is backed by SQL calls, instead
implement {@link MultiConverter} yourself.
stroom-db-util/src/main/java/stroom/db/util/ExpressionMapper.java