From the flows format documentation ( https://github.com/netobserv/network-observability-operator/blob/main/docs/flows-format.adoc ) , add a column about field availability in prometheus

For each field, this should tell one of:

• this field is available in default predefined metrics
• this field is available in non-default predefined metrics
• this field can be available via custom metrics (FlowMetrics API) (e.g. SrcK8S_Zone)
• this field can be available via custom metrics (FlowMetrics API) - but with a "high cardinality" warning (e.g. SrcK8S_Name)
• should not be used, or with extreme care (too high cardinality) (e.g. SrcAddr)