About api (#489)

* Add about-api doc

Signed-off-by: Jian Qiu <[email protected]>

* Add about-api doc

Signed-off-by: Jian Qiu <[email protected]>

---------

Signed-off-by: Jian Qiu <[email protected]>

Author: qiujian16

content/en/docs/concepts/cluster-inventory/clusterclaim.md

@@ -53,3 +53,91 @@ status:
     - name: id.k8s.io
       value: myCluster
 ```
+
+## About-API Support in Open Cluster Management
+
+Open Cluster Management (OCM) supports the use of `ClusterProperty` via the
+[about-api](https://github.com/kubernetes-sigs/about-api),
+which allows administrators to define and expose cluster-scoped properties. These properties are
+synced to the managed cluster's `ManagedCluster` status and can coexist with
+`ClusterClaim` but take precedence if a same-named property exists.
+
+### Enabling the Feature
+
+To enable the `ClusterProperty` feature on the spoke cluster, the `ClusterProperty` feature gate must be
+set on the Klusterlet component. This can be done by setting the feature gate in the Klusterlet configuration:
+
+```yaml
+featureGates:
+  ClusterProperty: "true"
+ ```
+
+Ensure that the feature gate is enabled appropriately based on your cluster management strategy.
+
+### Using ClusterProperty
+
+#### Creating a ClusterProperty
+
+Cluster administrators can create a `ClusterProperty` custom resource in the spoke cluster. The following
+is an example YAML for creating a `ClusterProperty`:
+
+```yaml
+apiVersion: about.k8s.io/v1alpha1
+kind: ClusterProperty
+metadata:
+  name: example-property
+spec:
+  value: "example-value"
+```
+
+Once created, the `ClusterProperty` will be automatically synced to the hub cluster and reflected within
+the `ManagedCluster` resource's status.
+
+#### Syncing Existing Properties
+
+After enabling the feature, any existing `ClusterProperty` resources will be synced to the `ManagedCluster`
+status on the hub cluster.
+
+Example: If `example-property` with value `example-value` already exists on the spoke cluster, its value
+will populate into the `ManagedCluster` as:
+
+```yaml
+status:
+  clusterClaims:
+    - name: "example-property"
+      value: "example-value"
+```
+
+#### Handling Conflicts with ClusterClaim
+
+In case a `ClusterClaim` resource with the same name as a `ClusterProperty` exists, the `ClusterProperty`
+will take precedence and the corresponding `ClusterClaim` will be ignored.
+
+#### Updating ClusterProperties
+
+Updating the value of an existing `ClusterProperty` will automatically reflect the change in the managed
+cluster's status:
+
+```yaml
+spec:
+  value: "updated-value"
+```
+
+#### Deleting ClusterProperties
+
+When a `ClusterProperty` is deleted from the spoke cluster, its corresponding entry in the `ManagedCluster`
+status is removed:
+
+```shell
+kubectl delete clusterproperty example-property
+```
+
+This will result in the removal of the `example-property` from the `ManagedCluster` status on the hub cluster.
+
+### Additional Notes 
+- Both `ClusterProperty` and `ClusterClaim` can co-exist, with `ClusterProperty` taking precedence in
+naming conflicts.
+- The feature uses the existing OCM infrastructure for status synchronization, ensuring minimal disruption to
+ongoing operations.
+- Ensure compatibility and testing in your environment before enabling the `ClusterProperty` feature gate in
+production settings.