[docs] add note about upgrading to 1.8.0 in openshift

docs/install-openshift.md

@@ -120,6 +120,33 @@ This issue is resolved in Datadog Operator bundle 1.4.2+. Use the OperatorHub UI
 For further help, contact [Datadog Support][7].
 
 
+### Datadog Operator 1.8.0 on OpenShift
+
+![Error after upgrading to 1.8.0 without removing the deprecated v1alpha1 from CRD](assets/openshift_1.8.0_crd_error.png)
+
+When upgrading from versions `<1.8.0` to Datadog Operator `1.8.0` of the Datadog Operator bundle provided to OperatorHub in OpenShift, one may encounter an error in the `InstallPlan` and/or `ClusterServiceVersion` due to the removal of the deprecated v1alpha1 CRD version:
+```
+Message: Risk of data loss updating "datadogagents.datadoghq.com": new CRD removes version v1alpha1 that is listed as a stored version on the existing CRD
+```
+
+It is therefore recommended to run the command below and only upgrade afterwards:
+
+```bash
+oc patch customresourcedefinitions datadogagents.datadoghq.com --subresource='status' --type='merge' -p '{"status":{"storedVersions":["v2alpha1"]}}'
+```
+
+For more details, see [Removing an old version][8] from the Kubernetes Custom Resources documentation. If this command was not run before the upgrade and you encountered the error, please follow the **Resolution** steps below.
+
+#### Resolution
+
+1. Remove `v1alpha1` from DatadogAgent CRD: `oc patch customresourcedefinitions datadogagents.datadoghq.com --subresource='status' --type='merge' -p '{"status":{"storedVersions":["v2alpha1"]}}'`
+2. Remove both `ClusterServiceVersion` (current and failed upgrade): `oc delete csv datadog-operator.v1.7.0 datadog-operator.v1.8.0`
+3. Remove the status from the `Subscription` to force a new reconciliation: `oc patch sub datadog-operator-certified --subresource='status' --type='json' -p='[{"op": "remove", "path": "/status"}]'`
+4. The reconciliation should lead to a new `ClusterServiceVersion` (identical to the one preceeding the upgrade). Depending on the `installPlanApproval`, you might have to approve the `InstallPlan`.
+5. Proceed with the upgrade normally from the OperatorHub.
+![Error after upgrading to 1.8.0 without removing the deprecated v1alpha1 from CRD](assets/openshift_1.8.0_upgrade.png)
+
+**Note**: During these steps, the Datadog Agents will keep running, ensuring your observability is not disrupted.
 
 [1]: https://catalog.redhat.com/software/operators/detail/5e9874986c5dcb34dfbb1a12#deploy-instructions
 [2]: https://olm.operatorframework.io/
@@ -128,5 +155,4 @@ For further help, contact [Datadog Support][7].
 [5]: https://app.datadoghq.com/organization-settings/api-keys
 [6]: https://app.datadoghq.com/organization-settings/application-keys
 [7]: https://www.datadoghq.com/support/
-
-
+[8]: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definition-versioning/