feat(contrib/opentelemetry): add TraceID and SpanID fields to the logger

[mlcdf]

Hello :)

What was changed

This PR adds the TraceID and the SpanID to the logger fields.

Why?

From the opentelemetry spec:

It is a standard practice to record the execution context (trace and span ids as well as user-defined context) in the spans. OpenTelemetry extends this practice to logs where possible by including TraceId and SpanId in the LogRecords. This allows to directly correlate logs and traces that correspond to the same execution context. It also allows to correlate logs from different components of a distributed system that participated in the particular request execution.

Checklist

2. How was this tested:

I added a test to make sure the fields are indeed present.

To test this, I needed a logger that could fill the log.Logger and I didn't wanted to add an extra dependency or roll out my own. So I relied on the new slog package (that's why I had to create new file and add the build annotation). Let me know if it's ok for you.

3. Any docs updates needed?

I'm not sure.

[CLAassistant]

All committers have signed the CLA.

[mlcdf]

I'm wondering if I should call HasTraceID/HasSpanID first

I'm not sure when they would be empty

[Quinn-With-Two-Ns]

We could add an IsValid() check If this is a concern. I don't believe this function will get called if ref is not valid

[Quinn-With-Two-Ns]

@mlcdf Thanks for the contribution! looks good to me. @cretz any comments?

[Quinn-With-Two-Ns]

I'll leave open for a couple days before merging if @cretz has any comments

[cretz]

LGTM.

I would originally be hesitant to add log multiple tags to all existing logs, but this is a good case for doing it and I can't see a good enough reason to provide an opt-out at this time.

[mlcdf]

When may I expect a new release of the sdk?

[cretz]

No exact time, but hopefully soon. In the meantime, you can depend on this commit (or go get + @master) in your go.mod.