@Override
    public void listClients(String organizationId, int page, int pageSize, IAsyncResultHandler<List<String>> handler) {
        throw new UnsupportedOperationException("Vert.x AsyncMap does not yet support iteration"); // TODO 1.5.x supports iteration.
    }
@author Marc Savy {@literal <marc@rhymewithgravy.com>}
gateway/engine/vertx-shareddata/src/main/java/io/apiman/gateway/engine/vertx/shareddata/SharedGlobalDataRegistry.java