private void markCacheEntryAsCached(ISignalReadStream<ApiResponse> cacheEntry, final CachingResourcesConfig config) {
        if(cacheEntry.getHead() != null && cacheEntry.getHead() instanceof ApiResponse && cacheEntry.getHead().getHeaders() != null) {
            HeaderMap responseHeaders = cacheEntry.getHead().getHeaders();
            responseHeaders.put("Cache-Control", "max-age=" + String.valueOf(config.getTtl()));
        }
    }
Set or overwrite Cache-Control header with ttl as max-age to mark the response as cached
@param cacheEntry
@param config
gateway/engine/policies/src/main/java/io/apiman/gateway/engine/policies/CachingResourcesPolicy.java