Add discussion around label normalisation. (#925)
Add discussion around label normalisation. (#925)

Per discussions at dev meeting after PromCon.

Also add 'service' to list of labels to avoid while I'm here.
ddfreyne/prometheus-docs,ddfreyne/prometheus-docs,chosenken/docs,chosenken/docs,prometheus/docs,chosenken/docs,chosenken/docs,ddfreyne/prometheus-docs,ddfreyne/prometheus-docs,prometheus/docs,prometheus/docs