v1beta2: Improve kmc status report by adding conditions

[apedriza]

Proposal for improve k0smotron Cluster status report

Currently, k0smotron Cluster controller does not have a clear report of the reconciliation status using standards kubernetes method like the use of conditions. This changes introduce a clearer status reportir using kubernetes conventions described here

The goal is to give the user the needed report without the need to check inner resources supporting the controlplane like the secrets, configmaps or statefulsets involved.

New conditions

This PR introduces conditions for reporting the current state of the k0smotron cluster. As kubernetes conventions states: Controllers should apply their conditions to a resource the first time they visit the resource. Following that, no matter the state of the k0smotron cluster reconciliation, the conditions will be reported.

New Condition	Description
Available	Describe cluster availability. It summarizes if the main conditions to consider a cluster is fully available are true: ControlPlaneFunctional, KubeconfigSecretAvailable and ControlPlaneExposed
Deleting	Describe if a cluster that is in a deleting phase
CertificatesAvailable	Describes if the certificates for the cluster has been created
ControlPlaneFunctional	Describes if the cluster is functional. We consider a cluster functional if the kube-system namespace exists in the workload cluster
KubeconfigSecretAvailable	Describes if the kubeconfig secret to access the cluster is availablke, i.e, it has been created
ControlPlaneExposed	Describes if the service which allows the access to the cluster workloads has populated its external address
ControlPlaneUpToDate	Describes if all the replicas for the cluster are up to date with the desired cluster spec
ControlPlaneScaling	Describes if the cluster is scaling up or down

New fields

• readyReplicas: can be used to check how many pods have a Ready condition (same as the readyReplicas field for the inner stateful set. This value, together with the Availability condition, can let the user know how many controlplane instance the load will be balanced across.
• updatedReplicas : same as updatedReplicas for the inner statefulset. Can led the user know how many replicas runs with the desired state.

Deprecated fields

On the other hand, in favor of new methods for status reporting, Ready condition and .status.ReconcileStatus will be removed in next releases. Currently deprecated and mantained for a while in order to allow back and forth conversions.

• Ready status presents ambiguity, given it is calculated from the check expected replicas == current ready control plane replicas. The readiness probe is calculated by running k0s status, but that does not guarantee the workload Cluster is fully functional. For that reason, and for more clarity of what the status field represents, Ready condition is substituted by Avaialble condition, which is calculated taking into account conditions that SHOULD guarantee cluster is ready.
• .status.ReconcileStatus is removed. It is currently used to store logs from the controller. We should be able to report the state of the k0smotron Cluster controller reconciliation by using conditions, which is the standard in kubernetes for reporting resource state.