Add missing metadata keys to monitoring port subsz JSON

[davidkemper]

Unlike the other *z (e.g., connz and varz), subsz is missing the server_id key.

It is also missing now.

There are probably other metadata fields that could be added, but these are the notable omissions.

Here is a recent subsz payload:

{
  "num_subscriptions": 0,
  "num_cache": 0,
  "num_inserts": 0,
  "num_removes": 0,
  "num_matches": 0,
  "cache_hit_rate": 0,
  "max_fanout": 0,
  "avg_fanout": 0
}

[derekcollison]

Also time, etc.

So server id and name and now fields.

[derekcollison]

And if we do not already an account filter arg we can send.

[matthiashanel]

@derekcollison I would make subsz work like all the others meaning return everything.
In a separate issue add account args to all were applicable.
That is add it to connz too

[derekcollison]

What do you mean everything? This is about subs but agree we need server id and name and now timestamp for request.

[matthiashanel]

I'll add the fields but also address #1357

/subs like /connz should return all subscriptions, irrespective of account.
Then I will also add an option to (/subsz and /connz to query by account) and expose via system events as well.

[derekcollison]

subsz is currently not a pageable destination, so you can not return any dynamic sized lists here.
Subsz totals should be for all accounts I agree, it may just be $G. Take care at holding the servers locks, probably snapshot s.accounts and go one by one asking them (or the sl) for the stats.