Surface errors for a metric somehow?

[wlach]

@fbertsch pointed out in a discussion on Slack that you can surface the errors related to a metric (in this particular case: https://dictionary.telemetry.mozilla.org/apps/firefox_ios/metrics/pocket_open_story_position) by following the looker explore here:

https://dictionary.telemetry.mozilla.org/apps/firefox_ios/metrics/glean_error_invalid_label

Worth considering whether we could do some automatic etl on this and warn users of a metric if there are problems. Or we could just document it on DTMO. Could probably use some holistic product thinking /cc @ecsmyth