Litestar: expose opentelemetry_exclude_spans like FastAPI does #287

FastAPIConfig.opentelemetry_exclude_spans (#185, #225) drops the ASGI receive and send spans. LitestarConfig has no equivalent. The comment above the FastAPI field says Litestar's instrumentor has no such parameter, but Litestar's OpenTelemetryConfig has had exclude_spans: list[Literal["receive", "send"]] | None since 2.22, and litestar-otl already requires litestar>=2.22. Since #279, LitestarOpenTelemetryInstrument builds that config itself, so the value only needs passing through.

What it saves

I measured this on litestar-sqlalchemy-template, GET /api/decks/{id}/. The test runs the full app with one ORM read and drives it through raw ASGI. The OTLP exporter is patched to encode spans and then drop them. Each request emits 6 spans: the server span, 2 http send spans, connect and 2 SELECT. Excluding the send and receive spans removes the 2 http send spans. Medians of 3 runs, in req/s:

That is about 75 µs per request with every request traced. The FastAPI template showed about 55 µs per request on the same endpoint.

Proposal

Add the same opentelemetry_exclude_spans field to LitestarConfig and pass it to LitestarOpenTelemetryConfig(exclude_spans=...). Keep the default empty, as on FastAPI, so existing trace views don't change. Update the FastAPI comment, and remove "FastAPI only" from the configuration and performance docs.