feat(tracing): propagate gcp trace header in tracing plugins

[jonabc]

Summary

This change parses and propagates the X-Trace-Context header that Google provides for calls in Google Cloud Projects (GCP). Google recommends using the OpenTelemetry tracing standard when instrumenting applications, and this provides handling of the header at the API gateway layer 👍

Checklist

• The Pull Request has tests
• There's an entry in the CHANGELOG
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - feat(opentelemetry): propagate GCP trace header docs.konghq.com#5829

Full changelog

• OpenTelemetry: Support GCP X-Cloud-Trace-Context header
  The field header_type now accepts the value gcp to propagate the
  Google Cloud trace header

Issue reference

I didn't see an open issue for this, but I'm happy to open an issue and link it here if wanted.

[CLAassistant]

All committers have signed the CLA.

[jonabc]

@hanshuebner 👋 I saw you gave a review on a similar PR for propagating AWS' xray trace headers, would you mind taking a look here as well? Sorry for the ping, this has been sitting around a little while and I'd love to have this included in Kong if possible 🙏

[hanshuebner]

@samugi Can you have a look? This seems to be right up your alley.

[samugi]

Thank you so much for your contribution!

I gave this a first pass, I'll be looking into the tests next but I have already left some comments that might suggest at least one missing test case.

[jonabc]

@samugi thanks for the feedback! I think I've addressed everything you brought up in 75344f1 (force-pushed to rebase on top of latest kong master). Would you mind taking another look?

[samugi]

Almost there, with these tiny changes it should be ready!

[jonabc]

@samugi thanks again! Updated (+ rebase on latest Kong:master) in e1b04fb. I also moved the changelog entry to unreleased, it looks like it was still set in 3.4.0.

Do you have any estimates on when 3.5.0 will be released, assuming this will go out with the next feature release?

[samugi]

assuming this will go out with the next feature release

@jonabc That is correct. I don't have a date to share yet but I expect 3.5.0 to be out roughly in 2-3 months considering 3.4.0 was just released. Again thanks so much for your contribution!

[outsinre]

Is this in EE?

[samugi]

It is now @outsinre