This pr update the way metrics with different label sets and the same name are stored in a collector.
If a new metric has a new label, this new label is added to the collector and all previous metrics in the collector get it with an empty string as its value.
Overview
This pr update the way metrics with different label sets and the same name are stored in a collector. If a new metric has a new label, this new label is added to the collector and all previous metrics in the collector get it with an empty string as its value.
What this PR does / why we need it
Closes #616
Special notes for your reviewer