private Throwable mapThrowable(Throwable throwable, RpcRequest<?> request) {
        // e.g. ClosedChannelException
        return new RuntimeException(
                "Failed to request a response for the request: "
                        + request,
                throwable);
    }
@return 1. a non-empty publisher that publishes an empty map if all peers respond with an
        empty payload; 2. a non-empty publisher that publishes a non-empty map if any peer
        responds with an non-empty valid payload; 3. error for other cases (e.g. no peer
        exists). The key is the member node ID, and the value is the response
turms-server-common/src/main/java/im/turms/server/common/infra/cluster/service/rpc/RpcService.java