Include username in detailed connection information.

[ebusto]

What motivated this proposal?

Our NATS cluster has a very small number of accounts, but each account has a number of distinct users. Being able to track traffic by user would be helpful when identifying heavy hitters.

What is the proposed change?

When collecting detailed connection information (when cardinality is already out the window), add auth=true as a query parameter when hitting the connz endpoint, and include the name_tag value in each corresponding metric.

Who benefits from this change?

Any NATS operator that wishes to track metrics per user, rather than (or in addition to) per account.

What alternatives have you evaluated?

Unfortunately splitting out our users into separate accounts would be a significant (breaking) change. I suspect we're not alone.