TraceLayer on_response: skip recording metrics if request was for healthcheck

[sdd]

Summary

I'm using TraceLayer's on_response handler to record latency metrics for a tonic service. I want to ignore requests that were for the healthcheck endpoint though, to avoid skewing the metrics.

I can't pull the request path from the span though because there doesn't seem to be a way to access span fields that have been previously added to the span.

What's the best approach for situations like this?

tower-http version

0.6.2