BSONObj BalanceChunkRequest::serializeToRebalanceCommandForConfig(const ChunkType& chunk) {
    invariantOK(chunk.validate());

    BSONObjBuilder cmdBuilder;
    cmdBuilder.append(kConfigSvrMoveChunk, 1);
    cmdBuilder.appendElements(chunk.toBSON());

    return cmdBuilder.obj();
}
BSONObj BalanceChunkRequest::serializeToMoveCommandForConfig(
    const ChunkType& chunk,
    const ShardId& newShardId,
    int64_t maxChunkSizeBytes,
    const MigrationSecondaryThrottleOptions& secondaryThrottle,
    bool waitForDelete) {
    invariantOK(chunk.validate());

    BSONObjBuilder cmdBuilder;
    cmdBuilder.append(kConfigSvrMoveChunk, 1);
    cmdBuilder.appendElements(chunk.toBSON());
    cmdBuilder.append(kToShardId, newShardId);
    cmdBuilder.append(kMaxChunkSizeBytes, static_cast<long long>(maxChunkSizeBytes));
    {
        BSONObjBuilder secondaryThrottleBuilder(cmdBuilder.subobjStart(kSecondaryThrottle));
        secondaryThrottle.append(&secondaryThrottleBuilder);
        secondaryThrottleBuilder.doneFast();
    }
    cmdBuilder.append(kWaitForDelete, waitForDelete);

    return cmdBuilder.obj();
}