InitBaseMetrics will initialize base, default metrics to 0 values.

InitConfigMetrics will init the "enable epochs" configuration metrics from epoch config.

InitMetrics will init metrics for status handler.

InitRatingsMetrics will init the ratings configuration metrics.

SaveStringMetric will save a string metric in status handler.

SaveUint64Metric will save an uint64 metric in status handler.

ErrNilAppStatusHandler signals that a nil app status handler instance has been provided.