Look for errors in the graphql response for metric tagging

[jjacobs44]

Pull Request type

• [x] Bugfix
• [ ] Feature
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Other (please describe):

Changes in this PR

It's possible to manually craft a DataFetcherResult and place errors within the error field. In the previous implementation, if your datafetcher were to catch all of its own exceptions and do this manual creation of a DataFetcherResult, those requests would not properly get tagged as a request which contained an error in metrics.

This changes the implementation to inspect the actual graphql result to check if it contains errors on top of just looking for exceptions.