HTTP headers for propagating trace and span context

[stevapple]

Is your feature request related to a problem? Please describe.
Trace and span context can be propagated through HTTP header(s). W3C has a recommended standard compatible with OpenTelemetry, while older Jaeger-compatible clients are using Uber's original format. If possible, we should support both:)

Describe the solution you'd like
Parse the HTTP headers accordingly and, if the content is valid, propagate the trace by overriding the default settings (trace id/parent span id/sampled/...).

Describe alternatives you've considered
Simply ignore it like what we're doing now. The full semantics is rather complex, so it may not worth the effort.

Additional context
https://www.w3.org/TR/trace-context-1/#trace-context-http-headers-format
https://www.jaegertracing.io/docs/1.22/client-libraries/#tracespan-identity

[Pierre-Lannoy]

Hi @stevapple and thanks for this suggestion.
From my point of view, it could be done (and it's an interesting point) based on the W3C recommandation. Nevertheless I am a bit more sceptical about the Jaeger format… Let me think about it.
There is also one thing I don't quite understand about the W3C recommendations: do you see something about "trace poisoning"?