[Feature Request]: Add timestamp argument to produce

[vtomskih]

Is your request related to a problem you have?

Confluent.Kafka producer allows to provide custom timestamp, but now we always use default Timestamp = Timestamp.Default. We want to be able to specify our own event timestamp.

Describe the solution you'd like

Add overloads to IMessageProducer with timestamp:

    Task<DeliveryResult<byte[], byte[]>> ProduceAsync(
        string topic,
        object messageKey,
        object messageValue,
        IMessageHeaders headers = null,
        int? partition = null,
        Timestamp timestamp = Timestamp.Default);

[PaulOberg1]

@vtomskih Hi, would be willing to help out and submit a PR. Could I be assigned if possible? Cheers