improve upgrade documentation and script

docs/upgrading.rst

@@ -48,6 +48,11 @@ The script does the following:
 #. Delete the ``oas`` and ``oas-apps`` namespace
 #. Create the new ``stackspin`` source and kustomization
 
+Because there are not many Stackspin users yet, the script can need some manual
+adjustments. It was written for clusters on which all applications are
+installed. If you have *not* installed some of the applications, please remove
+these applications form the script manually.
+
 .. code:: bash
 
    # Execute the upgrade preparation script
@@ -91,12 +96,20 @@ renamed from ``oas`` to ``stackspin``. You can choose from these options:
 Rocket.Chat
 ~~~~~~~~~~~
 
-We haven't found a way to keep your old Rocket.Chat history. Because we will
-soon `replace Rocket.Chat with Zulip
-<https://open.greenhost.net/stackspin/stackspin/-/issues/997>` we have not put
-energy into providing an upgrade path. If you want to upgrade Rocket.Chat
-without data loss, this should theoretically be possible with a ``mongodb``
-backup that you can restore into a database with a different hostname.
+It is possible to back-up and restore Rocket.Chat, but you have to do it
+manually. Before you run the ``rename-to-stackspin.sh`` script, you need to run
+a ``mongodump`` of the database inside the pod. After everything is done and
+you have re-installed Rocket.Chat, you need to restore the mongodump with
+``mongorestore``:
+
+
+.. code:: bash
+
+   # These commands need to be run *inside* the rocketchat-mongodb pod:
+   # To dump:
+   mongodump --db rocketchat  <backup_dir> -u root --authenticationDatabase admin
+   # To restore:
+   mongorestore --db rocketchat  <backup_dir>/backup/rocketchat/rocketchat -u root --authenticationDatabase admin
 
 Monitoring
 ~~~~~~~~~~

upgrade-scripts/to-0.8.0/rename-to-stackspin.sh

@@ -89,10 +89,6 @@ done
 # Remove old git repository
 flux delete --silent source git openappstack
 
-# Delete old namespaces
-kubectl delete ns oas
-kubectl delete ns oas-apps
-
-echo "Now check if all the Flux kustomizations and HelmReleases have disappeared. If they haven't, wait until they have. Then you can re-run the install-stackspin.sh script and after that, re-run install-apps.sh <app> for each app you want to (re)install."
+echo "Now check if all the Flux kustomizations and HelmReleases and the 'oas' and 'oas-apps' namespace have disappeared. If they haven't, wait until they have. Then you can re-run the install-stackspin.sh script and after that, re-run install-apps.sh <app> for each app you want to (re)install."
 
 echo "Refer to the upgrade guide <https://docs.stackspin.net/en/latest/upgrading.html> for app specific upgrades."