natssysclient: add server-scoped monitoring endpoints

[piotrpio]

Adds clients for missing SRV monitoring endpoints the library didn't previously cover, each exposed with a single-server method and a cluster-wide *Ping method

• Idz / IdzPing
• Routez / RoutezPing
• Gatewayz / GatewayzPing
• Leafz / LeafzPing
• Accountz / AccountzPing
• Profilez / ProfilezPing
• Expvarz / ExpvarzPing
• Ipqueuesz / IpqueueszPing
• Raftz / RaftzPing

Signed-off-by: Piotr Piotrowski piotr@synadia.com

[piotrpio]

@claude review this PR

[synadia-claude-reviewer]

Claude finished @piotrpio's task in 2m 8s —— View job

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PR Review: natssysclient: add server-scoped monitoring endpoints

• Read changed files and gather context
• Review API design and consistency
• Review implementation correctness
• Review tests
• Post review feedback

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Overall this is a well-structured, comprehensive addition that faithfully follows existing patterns. Tests are thorough and include both single-server and cluster-wide (Ping) variants. The implementation is clean and consistent. A few observations below.

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Issues

1. Pre-existing typo in ErrInvalidServerID — worth fixing while touching the file

api.go:41:

ErrInvalidServerID = errors.New("sever with given ID does not exist")

"sever" should be "server". This is pre-existing but the PR already modifies api.go, so it's a good opportunity to fix.

Fix this →

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2. Embedding order inconsistency in IpqueueszEventOptions and RaftzEventOptions

ipqueuesz.go:48-51 and raftz.go:82-85:

// Inconsistent — EventFilterOptions first
IpqueueszEventOptions struct {
    EventFilterOptions
    IpqueueszOptions
}

RaftzEventOptions struct {
    EventFilterOptions
    RaftzOptions
}

Every other *EventOptions type in the package places the domain-specific options first:

// Consistent pattern from routez.go, gatewayz.go, leafz.go, accountz.go, etc.
RoutezEventOptions struct {
    RoutezOptions
    EventFilterOptions
}

This doesn't affect correctness (JSON marshaling is field-name based, not order-based), but it's inconsistent with the established pattern.

Fix this →

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Minor Notes

ProfilezOptions.Duration serialization — time.Duration serializes as a nanosecond int64 in JSON, which matches what the NATS server expects. No issue, just confirming this is intentional and correct.

pingServers capacity pre-allocation (api.go) — the new if s.opts.serverCount > 0 { msgs = make(..., serverCount) } is a nice micro-optimization, good addition.

IdzPing takes no options — correct, since IDZ has no configurable parameters. The asymmetry with other *Ping methods (which all take an options struct) is expected and intentional here.

SubjectPermission defined in routez.go — it's also reused in leafz.go. Since both files are in the same package this is fine, though a dedicated types.go would be an alternative. Not a blocker.

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Summary

The PR is clean, well-tested, and follows existing conventions. The two issues above are worth addressing — the typo is a definite fix and the embedding-order inconsistency keeps the API surface predictable. Everything else looks good to go.