Add docs about how to adopt v1beta2

Signed-off-by: apedriza <adripedriza@gmail.com>

Author: apedriza

docs/update/migrate-v1beta2-api.md

@@ -0,0 +1,65 @@
+# Migrate to v1beta2 APIs
+
+This guide explains changes introduced in new `v1beta2` and how to migrate manifests from current `v1beta1` to the new k0smotron API.
+
+## Deprecation Policy
+
+Starting from `PLACCEHOLDER`, k0smotron uses new `v1beta2` API version as storage version and deprecate `v1beta1`, which still served for compatibility. K0smotron follows the [Kubernetes API deprecation policy](https://kubernetes.io/docs/reference/using-api/deprecation-policy/) for beta APIs:
+
+- `v1beta1` is deprecated once `v1beta2` is the preferred/storage version.
+- `v1beta1` will be removed no earlier than `max(9 months, 3 minor releases)` after deprecation.
+- Until removal, `v1beta1` may still be served via conversion webhooks.
+- After removal, clients must use `v1beta2`.
+
+## Changes per API group
+
+### k0smotron.io
+
+#### Cluster
+
+- Storage config was restructured:
+  - `spec.kineDataSourceURL` -> `spec.storage.kine.dataSourceURL`
+  - `spec.kineDataSourceSecretName` -> `spec.storage.kine.dataSourceSecretName`
+  - `spec.etcd` -> `spec.storage.etcd`
+  - New selector field: `spec.storage.type` with values `etcd`, `kine`, `nats`.
+- Now, a Cluster state is reported using conditions as Kubernetes conventions follows. Details about introduced conditions can be found [here](https://github.com/k0sproject/k0smotron/pull/1365). This implies:
+  - Move `Cluster` status reporting to Conditions.
+  - Deprecate legacy status fields such as `status.ready` and `status.reconciliationStatus`.
+- TODO: check fields that can be removed in favor of patches.
+  
+!!! note
+
+    Downgrade caveat: `nats` has no `v1beta1` equivalent and is dropped on conversion back to `v1beta1`
+
+#### JoinTokenRequest
+
+- No changes between versions.
+
+### bootstrap.cluster.x-k8s.io
+
+#### K0sControllerConfig and K0sWorkerConfig
+
+- `spec.ignition` and `spec.customUserDataRef` moved under `spec.provisioner`.
+- Renamed command fields:
+  - `spec.preStartCommands` -> `spec.preK0sCommands`
+  - `spec.postStartCommands` -> `spec.postK0sCommands`
+- Status moved from boolean ready flag to initialization struct:
+  - `status.ready` -> `status.initialization.dataSecretCreated`
+
+TODO: check CAPI changes 
+
+### controlplane.cluster.x-k8s.io
+
+#### K0sControlPlane
+
+TODO: check CAPI changes 
+
+- Status fields aligned to CAPI v1beta2 style:
+  - `status.updatedReplicas` -> `status.upToDateReplicas`
+  - `status.unavailableReplicas` replaced by `status.availableReplicas`
+  - `status.initialized` -> `status.initialization.controlPlaneInitialized`
+- Several status counters are now optional pointers (may be unset early in reconciliation).
+
+### infrastructure.cluster.x-k8s.io
+
+TODO: check CAPI changes 

mkdocs.yml

@@ -55,6 +55,7 @@ nav:
      - Cluster API (HCP): update/update-cluster-pod.md
      - Cluster API (VMs): update/update-capi-cluster.md
      - Update workers (HCP): update/hcp-autopilot.md
+     - Migrate to v1beta2 API: update/migrate-v1beta2-api.md
   - FAQ: faq.md
   - Troubleshooting: troubleshooting.md
   - Commercial Support: commercial-support.md