Wrap /upstream/{upstreamPath...} in the metrics middleware so activity
log entries are recorded for model-dispatched endpoints accessed through
the upstream passthrough.
- Move findModelInPath to shared.FindModelInPath and reuse it in
handleUpstream, the log monitor lookup, and FetchContext.
- Extend FetchContext to resolve the model from /upstream/<model>/...
paths without consuming the request body.
- Add isMetricsRecordPath to limit recording to the model-dispatched
endpoints that produce token usage/timings.
- Add tests for upstream metrics recording and FetchContext upstream
path resolution.
Fixes#855
Benson Wong
a15e47922c