support propagation of incoming requests

[LeTamanoir]

What is the problem this feature would solve?

If I call an Elysia app from a another app that forwards a traceparent, elysia does not pick it up.

https://opentelemetry.io/docs/languages/js/propagation/#manual-context-propagation

What is the feature you are proposing to solve the problem?

Add support for incoming request propagation

What alternatives have you considered?

No response

[LeTamanoir]

I believe to make this work this part of the code:

opentelemetry/src/index.ts

Lines 271 to 277 in c9f771c

	tracer.startActiveSpan('request', (rootSpan) =>
	otelContext.bind(
	trace.setSpan(otelContext.active(), rootSpan),
	fn
	)
	)
	)

should be adapted to be able to receive the request headers, and create the context from the headers.

something like this:

import { propagation } from '@opentelemetry/api';

[...]

.wrap((fn, find_a_way_to_pass_headers_of_request) =>
  tracer.startActiveSpan('request', (rootSpan) =>
    otelContext.bind(
      trace.setSpan(propagation.extract(otelContext.active(), headers_of_request), rootSpan), fn
    )
  )
)