docs: public CompletableFuture<Long> appendEntries() {
      raft.checkThread();
  
      // If there are no other active members in the cluster, simply complete the append operation.
      if (raft.getCluster().getRemoteMemberStates().isEmpty()) {
        return CompletableFuture.completedFuture(null);
      }
  
      // Create a heartbeat future and add it to the heartbeat futures list.
      TimestampedFuture<Long> future = new TimestampedFuture<>();
      heartbeatFutures.add(future);
  
      // Iterate through members and append entries. Futures will be completed on responses from followers.
      for (RaftMemberContext member : raft.getCluster().getRemoteMemberStates()) {
        appendEntries(member);
      }
      return future;
    }