public Mono<Map<String, Integer>> countOnlineUsersByNodes() {
        CountOnlineUsersRequest request = new CountOnlineUsersRequest();
        return node.getRpcService()
                .requestResponsesAsMapFromOtherMembers(request, false)
                .onErrorResume(
                        throwable -> RpcException.isErrorCode(throwable,
                                RpcErrorCode.MEMBER_NOT_FOUND),
                        throwable -> PublisherPool.emptyMap());
    }
@implNote Note that the count requests are sent by turms but all responses should come from
          turms-gateway so we don't need to count the local online users like ".map(count ->
          count + countLocalOnlineUsers())"
turms-service/src/main/java/im/turms/service/domain/observation/service/StatisticsService.java