Refactor the prometheus initializer
Refactor the prometheus initializer

Just inline the metrics names so one can easily find them

e.g. `"git_fetch_duration_seconds"` vs `"git_#{operation}_duration_seconds"`

FundingCircle/shipment_tracker,FundingCircle/shipment_tracker,FundingCircle/shipment_tracker,FundingCircle/shipment_tracker