Metrics scope for invoicing

Source: Invoicing adapter
Stimulus: Calculate invoice
Environment: APPUiO Cloud Global
Artifact: Metric storage for invoicing
Response: A time series of usage metrics
Response measure: A time series is returned per pod.
Rationale: Users manage their workload on the level of pods through Kubernetes Deployments and StatefulSets. However, OpenShift 4 collects metrics on the level of containers within pods. Summarizing the data at the pod level allows to present the data in a familiar way to the user.