Cluster update metrics

Metrics that are used to generate cluster update alerts are added to the alerting rules in /var/lib/prometheus/alerts/backend.rules. These metrics are described in the table:

Metric	Description	Labels
`softwareupdates_cluster_info`	Information about software updates for the cluster	`available_version` Available version for the cluster `impact` Update impact: `reboot`: reboot is required during the update `maintenance`: maintenance is required during the update `no_impact`: reboot and maintenance are not required during the update `state` Update state for the cluster `version` Currently installed version for the cluster
`softwareupdates_cluster_available`	Update availability for the cluster	`available_version` Available version for the cluster `impact` Update impact: `reboot`: reboot is required during the update `maintenance`: maintenance is required during the update `no_impact`: reboot and maintenance are not required during the update `version` Currently installed version for the cluster
`softwareupdates_node_uptodate`	Shows if a specific node is updated to the latest version	`available_version` Available version for a node `impact` Update impact: `reboot`: reboot is required during the update `maintenance`: maintenance is required during the update `no_impact`: reboot and maintenance are not required during the update `node` Node ID `version` Currently installed version for a node
`softwareupdates_node_available`	Update availability for a specific node	`available_version` Available version for a node `impact` Update impact: `reboot`: reboot is required during the update `maintenance`: maintenance is required during the update `no_impact`: reboot and maintenance are not required during the update `node` Node ID `version` Currently installed version for a node
`softwareupdates_node_info`	Information about software updates for a specific node	`available_version` Available version for a node `impact` Update impact: `reboot`: reboot is required during the update `maintenance`: maintenance is required during the update `no_impact`: reboot and maintenance are not required during the update `node` Node ID `state` Update state for a node `version` Currently installed version for a node
`softwareupdates_node_state`	Update state of a specific node	`node` Node ID `state` Update state of a node