Change http.request.body.size and http.response.body.size attributes from recommended to opt-in

[mateuszrzeszutek]

Implements open-telemetry/semantic-conventions#460

[trask]

heads up, I think my proposed change open-telemetry/semantic-conventions#461 would result in deleting the code (but makes sense to keep it until then)

[mateuszrzeszutek]

Hmm, the body size metrics too?
The only reason I introduced an experimental attributes extractor is to keep the experimental metrics working

[trask]

Hmm, the body size metrics too?

I'm not sure, it's a good question, maybe we need *.header.content_length metrics, or maybe we could relax the metric definition to allow populating it just from content-length header

The only reason I introduced an experimental attributes extractor is to keep the experimental metrics working

👍

[mateuszrzeszutek]

maybe we could relax the metric definition to allow populating it just from content-length header

Metric definition is one thing -- the limiting factor here is the OperationListener interface, actually. We can only produce metrics from Context and Attributes unfortunately