Unable to access application context in discovery

Describe the bug
Though I fixed the documentation in https://github.com/spring-cloud/spring-cloud-gateway/pull/2733 I am still unable to use the rate limiter in Discovery. It appears that in the code you're assembling a new evaluation context containing only the metadata and not include the rest of the context so defining a keyresolver does not work inside discovery

In DiscoveryClientRouteDefinitionLocator specifically

	private DiscoveryClientRouteDefinitionLocator(String discoveryClientName, DiscoveryLocatorProperties properties) {
		this.properties = properties;
		if (StringUtils.hasText(properties.getRouteIdPrefix())) {
			routeIdPrefix = properties.getRouteIdPrefix();
		}
		else {
			routeIdPrefix = discoveryClientName + "_";
		}
               // context is built here
		evalCtxt = SimpleEvaluationContext.forReadOnlyDataBinding().withInstanceMethods().build();
	}

// and only gets the info from the service instance.

	String getValueFromExpr(SimpleEvaluationContext evalCtxt, SpelExpressionParser parser, ServiceInstance instance,
			Map.Entry<String, String> entry) {
		try {
			Expression valueExpr = parser.parseExpression(entry.getValue());
			return valueExpr.getValue(evalCtxt, instance, String.class);
		}
		catch (ParseException | EvaluationException e) {
			if (log.isDebugEnabled()) {
				log.debug("Unable to parse " + entry.getValue(), e);
			}
			throw e;
		}
	}

Sample
If possible, please provide a test case or sample application that reproduces
the problem. This makes it much easier for us to diagnose the problem and to verify that
we have fixed it.

Start in DiscoveryClientRouteDefinitionLocator, especially its evaluation-context construction and getValueFromExpr, and reproduce the rate-limiter keyresolver case described in the issue. Done means expressions used for discovery routes can access the required application context rather than only ServiceInstance metadata, with a regression test or sample reproducing the reported behavior.