Add per quest customized attribute to http metrics instrumentation

[NickiHua]

Problem Statement

We are trying to add instrumentation to our http server and client with go opentelemetry http instrumentation. Our caller will have some special header sets indicating the caller identity and we would like to emit that in the http metrics, e.g. http.server.duration then we can have statistics of the latency for the specific user.

It looks like labeler can only set some static customized attributes but not per request attributes.

Is there a way to do that? Let the meter to read the http request header and set that in the metrics for every request? Or we have to implement our own otel http instrumentation?