storage: Use Authelia for Longhorn UI auth

Instead of using a static username/password and HTTP Basic
authentication for the Longhorn UI, we can now use Authelia via the
*nginx* auth subrequest functionality.

storage/README.md

@@ -23,18 +23,11 @@ kubectl apply -f longhorn.yaml
 Expose the Longhorn UI outside the cluster:
 
 ```sh
-printf 'Longhorn username: '
-read longhorn_username
-printf 'Longhorn password: '
-read -s longhorn_password
-printf '%s:%s\n' \
-    "${longhorn_username}" \
-    "$(openssl passwd -stdin -apr1 <<< "${longhorn_password}")" \
-    > auth
-kubectl create secret generic -n longhorn-system basic-auth --from-file auth
 kubectl apply -f longhorn-ingress.yaml
 ```
 
+Authentication to the UI is handled by Authelia.
+
 
 [0]: https://longhorn.io/docs/1.3.0/deploy/install/install-with-kubectl/
 [1]: https://longhorn.io/docs/1.3.0/advanced-resources/deploy/node-selector/