Add breaking changes doc for 2.6.0 (#3802)

* Add breaking changes doc

* Update docs/hugo/content/guide/breaking-changes/breaking-changes-v2.6.0.md

Co-authored-by: Bevan Arps <[email protected]>

---------

Co-authored-by: Bevan Arps <[email protected]>

docs/hugo/content/guide/breaking-changes/breaking-changes-v2.6.0.md

@@ -0,0 +1,22 @@
+---
+title: "v2.6.0 Breaking Changes"
+linkTitle: "v2.6.0"
+weight: 70
+---
+
+## VirtualMachineScaleSet ProtectedSettings now a SecretReference
+
+The property `VirtualMachineProfile.ExtensionProfile.Extension.ProtectedSettings` on `VirtualMachineScaleSet` has been changed from a string to a `SecretReference`
+We always try to avoid breaking changes, but in this case, allowing raw passwords in the spec is a security problem and as such we've
+decided to make a break to correct this issue.
+
+**Action required:** If the `Compute/VirtualMachineScaleSet` resource is used in your cluster and the `VirtualMachineProfile.ExtensionProfile.Extension.ProtectedSettings` property is set, do the following before upgrading ASO:
+
+1. Annotate the resource with `serviceoperator.azure.com/reconcile-policy: skip` to prevent ASO from trying to reconcile the resource while you are upgrading.
+2. Download the current YAML for the resource using `kubectl` if you don't have it elsewhere.
+3. Create a kubernetes secret containing the value for `VirtualMachineProfile.ExtensionProfile.Extension.ProtectedSettings`.
+4. Edit downloaded YAML in step 2, and add a secret key and name reference. Example [here](https://github.com/Azure/azure-service-operator/blob/main/v2/samples/apimanagement/v1api20230501preview/v1api20230501preview_authorizationprovider.yaml#L12).
+5. Delete the resource from your cluster using `kubectl delete`. Your Azure resource will be left untouched because of the `reconcile-policy` annotation you added above.
+6. [Upgrade ASO]( {{< relref "upgrading" >}} ) in your cluster.
+7. Apply the updated YAML to your cluster using `kubectl apply`. If any errors occur, address them.
+8. If the `reconcile-policy` annotation is still present, remove it from the resource.