ErrorCode returned by SPU is not reported in `RecordMetadata

[morenol]

if we do

    let future_record_metadata = producer.send(key, value).await?;
    let record_metadata = future_record_metadata.wait().await?;

If there is an error sent by the spu, it is not being reported.

Expected behavior:

    let record_metadata = future_record_metadata.wait().await?;

in case of error code, this should trigger a FluvioError with the associated error code