Error tag for auto instrumented XHRs

[kushaljh]

I am enabling xhr_instrumentation to help me get traces for the frontend of my application and I do get error logs for 400 and 500 level errors in the span logs but it would be helpful to also get an error: true tag in the same way as the span logs are being automatically populated.

The explorer does not support filtering by logs and also does not recognize errors in the logs.

This would be really helpful.

Thank you! :)

[sbaum1994]

Thanks again @kushaljh for filing this issue. Thoughts @bg451 @austinlparker ? Could/should this be added as an additional option? Some of our users don't always recognized 400 as an error so I wouldn't want to require that always, but almost everyone recognizes 500 as an error on their spans.