Does not work with the ambassador/envoy/lightstep integration

[martincognite]

The lightstep tracing module in envoy/ambassador passes down the headers x-ot-span-context and x-request-id, none of which work with the custom tracer.extract() function.

Renaming x-request-id to ot-tracer-traceid is not an issue, but I'm not sure how to decode x-ot-span-context into something useful (assuming it's not ot-tracer-spanid).

[ethanrubio]

The x-ot-span-context is a base64 encoded protobuf, so you'll need to do something like this https://github.com/austinlparker/lightstep-js-envoy-extract/blob/master/src/envoyPropagator.ts until it's properly supported in this tracer.