AbstractRateLimitFilter improvements about spring-cloud-zuul-ratelimit

[Aloren]

1. The main reason behind that change is that AbstractRateLimitFilter knows too much. It does all policies filtering: userApply, originApply, urlApply. I propose to extract these methods to separate simple filters and to use in AbstractRateLimitFilter only compound policy filter.
   Instead of:

    protected List<Policy> policy(Route route, HttpServletRequest request) {
...
        return policyMap.values().stream()
            .filter(policy -> compoundPolicyFilter.filter(request, route, policy))
            .collect(Collectors.toList());
    }

whereas PolicyFilter would look like this:

@RequiredArgsConstructor
public class OriginPolicyFilter implements PolicyFilter {
    private final RateLimitUtils rateLimitUtils;

    @Override
    public boolean filter(LinkedHashSet<String> originMatchers, HttpServletRequest request, Route route) {
        return originMatchers.isEmpty()
                || originMatchers.contains(rateLimitUtils.getRemoteAddress(request));
    }

    @Override
    public RateLimitProperties.Policy.Type getType() {
        return RateLimitProperties.Policy.Type.ORIGIN;
    }
}

It is just an idea, interfaces can be different. The main point is that adding new filter will not require touching AbstractRateLimitFilter. Moreover changing default logic behind these filtering logic wight now is impossible.
2,3. these points are actually about one thing -- having separate configuration index class instead of iterating on configuration each time, so changing current configuration won't be needed.

is the empty check neccessary?
is that about urls.isEmpty()? it is an existing code, i suppose that it is not needed.

[lchayoun]

1. Can you explain a bit more on the purpose of the custom filter.
2. It will be a good change, just need to keep the configuration as is and move the data to a set after initialization.
3. Also good change, is the empty check neccessary?

[lchayoun]

I see, sounds good.

[marcosbarbero]

@Aloren are you willing to work on this?

[lchayoun]

@Aloren @marcosbarbero I think that we did most of the changes in #100
Do you see anything we've missed?

[marcosbarbero]

Closing due to inactivity.