Get opentelemetry trace id from request headers instead of creating a new trace

[kozistr]

What does this PR do?

Fixes #2376

I made a simple middleware to extract OpenTelemetry context (e.g. trace id, span id) from request headers. When valid transparent info is provided, then, it'll gonna use that context to create the span (if not, it'll generate its own as it does currently).

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@OlivierDehaene OR @Narsil

[kozistr]

@Narsil @OlivierDehaene @ErikKaum hi! if you have the bandwidth, could you by any chance review this PR? thanks!

related PR: huggingface/text-embeddings-inference#425

[OlivierDehaene]

Sorry I was confused.
We already have a context extractor that we set here. It should already parse the W3C format and therefore the traceparent header so I'm not sure what exactly is the problem here.
Let me get back to you.

[kozistr]

Sorry I was confused. We already have a context extractor that we set here. It should already parse the W3C format and therefore the traceparent header so I'm not sure what exactly is the problem here. Let me get back to you.

Hi. Thanks for the response.

from these two comments, #2376 (comment), #2376 (comment), I guess it seems the axum opentelemetry integration doesn't just do it automatically unlike most other frameworks. So, I just made a simple middleware to parse the traceparent header and manually inject it. please let me know if you find a better way to implement this!