public Optional<RawFlag> resolve(FetchVector fetchVector) {
        return rules.stream()
                .filter(rule -> rule.match(defaultFetchVector.with(fetchVector)))
                .findFirst()
                .flatMap(Rule::getValueToApply);
    }
A data structure containing all data for a single flag, that can be serialized to/from JSON,
and that can be used to implement {@link FlagSource}.

@author hakonhall
flags/src/main/java/com/yahoo/vespa/flags/json/FlagData.java