fix(rest): close internally owned transports

[fallintoplace]

Summary

• retain the cleanup callback for the final REST session
• close catalog-owned HTTP and OAuth transports from Catalog.Close
• keep caller-provided transports caller-owned
• make session cleanup idempotent

Why

createSession builds cleanup callbacks for internally allocated transports, but initialization discarded the callback for the final long-lived session. Closing a catalog therefore left its idle connection pools alive.

Testing

• go test ./catalog/rest

[laskoviymishka]

Nice catch on the leak — throwing away createSession's cleanup with _ in init meant the long-lived session's internally-owned transports never got drained, and routing that cleanup through Close() behind a sync.Once (while leaving caller-provided transports alone) is exactly the right shape.

Almost there. One blocking thing before merge: the new test doesn't actually exercise the fix. It builds a Catalog literal with closeSession already set, so it only proves the sync.Once wrapper fires once — the line that fixes the bug (r.cl, r.closeSession, err = r.createSession(...)) is outside its scope, and reverting that line keeps the test green. For a regression test on a resource leak, I'd want it to fail if the wiring regresses, so I'd build a real catalog through the constructor with an internally-owned transport and assert CloseIdleConnections actually ran.

A couple of smaller things I'd want alongside that:

• reporter.Close() sits outside the Once, so it fires on every call. Not a bug today since CachedReporter is idempotent, but I'd fold it into the Once so the whole method is idempotent as one unit, and note that in the godoc.
• The catalog.Closer godoc in catalog/catalog.go still calls a stateful HTTP-backed closer a "future" thing — this PR makes it present, so that line is now stale.

Once the test actually pins the fix, happy to take another pass and approve.

[laskoviymishka]

This test doesn't actually exercise the fix.

It constructs a Catalog literal with closeSession already populated, so all it proves is that the sync.Once wrapper fires the callback once. The one line that fixes the leak — r.cl, r.closeSession, err = r.createSession(ctx, ops) in init — is entirely outside its scope. Revert that back to r.cl, _, err = ... and this test still passes green, which is exactly the regression we'd want it to catch.

I'd add an integration-level test that builds a real catalog through NewCatalog/newCatalogFromProps with an internally-owned transport, calls cat.Close(), and asserts that transport's CloseIdleConnections ran — closeTrackingTransport is already right there. And while we're in here, it'd be worth mirroring TestFetchConfigDoesNotCloseCustomTransport for Close(): build a catalog WithCustomTransport(base), close it, assert base.closed stays false, so the caller-ownership boundary is pinned too. Right now that invariant is only documented, not tested.

[laskoviymishka]

reporter.Close() sits outside the Once, so it fires on every Close() call while the session cleanup fires once.

It's not a live bug — CachedReporter.Close() is idempotent today (it nils itself under a mutex, so the second call is a no-op). But the new test advertises Close() as safe to call twice, and that guarantee currently leans on an undocumented property of the concrete reporter; a future non-idempotent or wrapped reporter breaks double-close callers quietly.

I'd pull reporter.Close() inside the Once so the whole method is idempotent as one unit, and capture the error:

func (r *Catalog) Close() error {
	var err error
	r.closeSessionOnce.Do(func() {
		if r.closeSession != nil {
			r.closeSession()
		}
		err = r.reporter.Close()
	})

	return err
}

The godoc could also mention Close is safe to call more than once, since that's now the intent (closeSessionOnce). wdyt?

[laskoviymishka]

Every other top-level test in this file calls t.Parallel() and there's no shared state forcing this one to be serial — I'd add it as the first line to stay consistent (and keep paralleltest happy if it's enabled).