docs: public CompletableFuture<Void> snapshot() {
      return Futures.allOf(config.getMembers().stream()
          .map(MemberId::from)
          .map(id -> communicationService.send(snapshotSubject, null, id, SNAPSHOT_TIMEOUT))
          .collect(Collectors.toList()))
          .thenApply(v -> null);
    }