docs: add cluster object store

docs/src/topics/cluster-object-store.md

@@ -0,0 +1,52 @@
+# Cluster Object Store
+
+The Cluster Object Store is an optional setting in the `LinodeCluster` resource definition that references an object
+storage bucket used for internal cluster operations. Currently, the Cluster Object Store feature enables the following capabilities:
+
+- Bypassing bootstrap data limits during Linode provisioning
+
+A [Linode Object Storage](https://www.linode.com/docs/guides/platform/object-storage/) bucket and access key are
+provisioned as the Cluster Object Store for each `LinodeCluster` resource with any of the `*-full` flavors. BYOB (Bring
+Your Own Bucket) may be used instead, by modifying a `LinodeCluster` definition:
+
+```yaml
+apiVersion: infrastructure.cluster.x-k8s.io/v1alpha2
+kind: LinodeCluster
+metadata:
+name: ${CLUSTER_NAME}
+spec:
+  objectStore:
+    credentialsRef:
+      name: ${CLUSTER_NAME}-object-store-credentials
+```
+
+to reference any Secret containing a object storage bucket's credentials in the following format:
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: ${CLUSTER_NAME}-object-store-credentials
+data:
+  bucket_name: ${BUCKET_NAME}
+  # Service endpoint
+  # See: https://docs.aws.amazon.com/general/latest/gr/s3.html
+  s3_endpoint: ${S3_ENDPOINT}
+  access_key: ${ACCESS_KEY}
+  secret_key: ${SECRET_KEY}
+```
+
+## Capabilities
+
+### Bootstrap Data Limits During Linode Provisioning
+
+Currently, during `LinodeMachine` bootstrapping, CAPL delivers the bootstrap data generated by a [bootstrap
+provider](https://cluster-api.sigs.k8s.io/developer/providers/bootstrap) to it's infrastructure Linode via one of the
+following services:
+
+| Service                                                                                       | Bootstrap Data Limit                                                                                 |
+| --------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------ |
+| [Metadata](https://techdocs.akamai.com/cloud-computing/docs/overview-of-the-metadata-service) | [65535 bytes](https://techdocs.akamai.com/linode-api/reference/post-linode-instance)       |
+| [Stackscripts](https://www.linode.com/products/stackscripts/)                                 | [65,535 characters](https://techdocs.akamai.com/linode-api/reference/post-linode-instance) |
+
+These data limits are bypassed when the Cluster Object Store feature is enabled.