Publish a Grafana template for Kea statistics

Many operators who are monitoring multiple systems prefer to have a single dashboard from which they can monitor all those systems at once.

It would be nice to have a template for the Grafana visualization system that is organized to help Kea operators quickly scan their system status and identify any anomalous traffic patterns. Then users who are using Grafana for monitoring other systems can just switch over to look at the Kea window.

This is not Kea development, it is a separate, but small, project, to produce a template and publish it.

Things users would like to be able to see at a glance:

• requests & leases per subnet over time (so you can see usage patterns)
• leases by address type (dynamic, static, prefixes)
• if possible, leases per address pool size (so you can see pool utilization go up and down) (I dk if we can get pool size via the stats)
• IPv4 vs IPv6 usage
• the time to respond (I dk the name of this stat but I know we monitor it as part of the HA feature)
• per server and possibly, aggregated over multiple servers?
• ha/failover status changes

If we also develop and support a Prometheus exporter, Prometheus has a plug-in for Grafana, so the whole system would be nicely integrated. https://grafana.com/plugins/prometheus

This feature was requested by an ISC Kea support customer.