Updated documentation for dex on k8s when RBAC authorization is used

Documentation/kubernetes.md

@@ -60,6 +60,7 @@ To run dex on Kubernetes perform the following steps:
 2. Spin up a Kubernetes cluster with the appropriate flags and CA volume mount.
 3. Create a secret containing your [GitHub OAuth2 client credentials][github-oauth2].
 4. Deploy dex.
+5. Create and assign 'dex' cluster role to dex service account (if RBAC authorization is used).
 
 The TLS assets can be created using the following command:
 
@@ -83,12 +84,14 @@ $ kubectl create secret \
     --from-literal=client-secret=$GITHUB_CLIENT_SECRET
 ```
 
-Finally, create the dex deployment, configmap, and node port service.
+Create the dex deployment, configmap, and node port service.
 
 ```
 $ kubectl create -f dex.yaml
 ```
 
+Assign cluster role to dex service account so it can create third party resources [Kubernetes third party resources](storage.md).
+
 __Caveats:__ No health checking is configured because dex does its own TLS termination complicating the setup. This is a known issue and can be tracked [here][dex-healthz].
 
 ## Logging into the cluster