feat(server-utils): Implement orchestrion-based express integration

[mydea]

Closes #20917

This adds a new expressChannelIntegration based on orchestrion. It should keep feature parity — we have a lot of Express tests, and the core tracing tests now run against this integration (via the orchestrion variant), which gives good coverage for now.

A follow up would be to also handle the error handler automatically where possible.

Route resolution: metadata is only set for genuinely matched routes

The OpenTelemetry Express integration patches every layer's handle, reconstructs the route from the layers that ran (getConstructedRoute), and validates it against the request URL (getActualMatchedRoute) to discard paths that didn't truly match.

This integration instead hooks Express's per-layer Layer.prototype.handle_request (v4) / handleRequest (v5, the router package). Express only calls that method for a layer whose path and method matched, so a request_handler span only ever exists for a route that genuinely matched. Route metadata — http.route, the root http.server span's route attribute, and the transaction name — is therefore taken directly from the matched route, with no separate reconstruct/validate step.

The observable consequence, which is intentional:

• 404 / no route matched — no route-dispatch layer runs, so no request_handler span is created and no route (or route-based transaction name) is set.
• Only middleware ran (no route matched) — middleware produces middleware-type spans, which never set route attributes.

This is a different mechanism from the OTel path, but it lands on the same net result: getActualMatchedRoute returns undefined in exactly these cases, so the OTel integration also emits no route there. We get it structurally, from the injection point, rather than by validating after the fact.

[cursor]

Transaction name before ignore check

Medium Severity

For ignored request-handler layers, the orchestrion path still calls setTransactionName before isLayerIgnored returns. The OTel patchLayer path sets the transaction name only after the ignore check, so ignoreLayers / ignoreLayersType can leave a transaction renamed without the matching span.

 

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[mydea]

this is more correct now IMHO

[cursor]

Express options not wired

Medium Severity

Orchestrion mode registers expressChannelIntegration() with no options while replacing the default OTel Express integration. User ignoreLayers and ignoreLayersType settings on expressIntegration never reach the channel integration, so layer filtering lacks parity with the OTel path.

 

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[mydea]

this is normal, if you pass in the express channel intergation manually it will overwrite

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 3 total unresolved issues (including 2 from previous reviews).

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