Set error attribute when encountering an error with a span

[NLincoln]

👋 we've been using zio-open-telemetry with DataDog for a bit. One weird thing we've been noticing is that our error spans don't show up as having errored in the DataDog UI. I think this is because DD expects

span.setAttribute("error", true)

When you encounter an error, which zio-open-telemetry doesn't do currently. Is there interest in adding those to zio-telemetry, probably in here? https://github.com/zio/zio-telemetry/blob/7e6e29c60ad4d9a72c03b175f598fb51f00ea693/opentelemetry/src/main/scala/zio/telemetry/opentelemetry/Tracing.scala#L56

[runtologist]

Yes, this looks good. Would you mind adding a test and un-drafting?

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Nathan Lincoln seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[n3ziniuka5]

I think the actual problem is on line 55:

val errorStatus: StatusCode = cause.failureOption.flatMap(toErrorStatus.lift).getOrElse(StatusCode.UNSET)

If you change StatusCode.UNSET to StatusCode.ERROR then you don't need any additional attributes and the errored traces appear as expected in Datadog.

[NLincoln]

Closing this PR - I no longer work with ZIO (changed jobs) so I won't be able to put the time in to finish it - sorry for leaving it open for so long :disappointed: