kafka: support dynamic quotas

[rkruze]

Today we limit based on a per client id, which is a single setting for the whole server. It would be ideal to set a quota on a per-user basis on either byte, requests, or network throughput. This would be similar to how quotas are set in Kafka today. https://kafka.apache.org/documentation/#design_quotasconfig

Some examples of how this is set in Kafka can be found here: https://github.com/JNachtwey/kafka-cheat-sheets/blob/master/kafka-quotas.md

JIRA Link: CORE-576

[dotnwat]

@rkruze now that we have users and ACLs etc... I think we are in a position to schedule this feature work.

[mattschumpert]

@dotnwat can you verify that there is indeed throttling per client id. This does not appear to be documented and itself is very useful (though per true tenant is of course needed as well)

[mattschumpert]

NM I found it

[dotnwat]

@michael-redpanda @BenPope seems like we might support per-user quota now, right?

[mattschumpert]

Still based on Client ID AFAIK, right @BenPope ? I agree this would be super valuable

[michael-redpanda]

We support client ID based but it's per shard rather than node. There's already an issue somewhere to address that

[michael-redpanda]

https://github.com/redpanda-data/core-internal/issues/785