MetricsInstrumentation: support differentiating queries with errors

[xialin]

Currently graphql.timer.query.* collect all queries regardless of response details. In particular, if a GraphQL query returns some errors, I cannot identify them from the metrics (metric name or tags).

Is it possible to add an error tag if executionResult.getErrors() is not empty? That way, I'll be able to check the error rate of my GraphQL queries.

Otherwise, I'd appreciate if anyone can share an alternative to capture error metrics.

Thanks!

[oliemansm]

Sounds like a nice improvement. Not sure when I'll get around to it myself though. We're also happy with any contributions in case you're able to create a PR for this yourself.