docs(issue_template): Improve rolling HDFS upgrade instructions

Author: Techassi

.github/ISSUE_TEMPLATE/pre-release-upgrade-testing.md

@@ -3,7 +3,7 @@ name: Pre-Release Demo Upgrade Testing
 about: |
   This template can be used to track the upgrade testing of demos from stable to
   nightly leading up to the next Stackable release.
-title: "chore(tracking): Test demo upgrades on nightly versions for YY.M.X"
+title: "tracking: Test demo upgrades to nightly versions for YY.M.X"
 labels: ['epic']
 assignees: ''
 ---
@@ -125,34 +125,30 @@ kubectl patch hbaseclusters/hbase --type='json' -p='[{"op": "replace", "path": "
 # Run through the (still) nightly demo/stack instructions again.
 ```
 
-### HDFS Rolling Upgrade
+<details>
+  <summary>HDFS rolling upgrade instructions</summary>
 
-For demos that use HDFS, also test a rolling upgrade.
-See <https://docs.stackable.tech/home/nightly/hdfs/usage-guide/upgrading/>.
+  ```shell
+  # In some cases (eg. in the end-to-end-security demo), HDFS is kerberized.
+  # This requires these commands to be run first.
+  # Pick "nn/..."
+  klist -kt /stackable/kerberos/keytab
+  kinit -kt /stackable/kerberos/keytab <PRINCIPAL_FROM_ABOVE>
 
-#### Prepare the upgrade (run in an HDFS superuser container)
+  # These commands need to be executed in a superuser environment (eg. the namenode pod)
+  hdfs dfsadmin -rollingUpgrade prepare
+  hdfs dfsadmin -rollingUpgrade query  # repeat until "Proceed with rolling upgrade"
 
-```shell
-hdfs dfsadmin -rollingUpgrade prepare
-hdfs dfsadmin -rollingUpgrade query  # repeat until "Proceed with rolling upgrade"
-```
-
-#### Patch the HdfsCluster to the new product version and wait for all pods to restart and reach Ready state
+  # Now patch the productVersion in your regular shell
+  kubectl patch hdfs/<CLUSTER_NAME> --type=merge \
+    --patch '{"spec": {"image": {"productVersion": "<NEW_VERSION>"}}}'
 
-```shell
-kubectl patch hdfs/<CLUSTER_NAME> --type=merge \
-  --patch '{"spec": {"image": {"productVersion": "<NEW_VERSION>"}}}'
-```
+  # Finalize the upgrade in the namenode pod
+  # Needs another kinit because the container was restarted
+  hdfs dfsadmin -rollingUpgrade finalize
 
-#### Finalize the upgrade (run in an HDFS superuser container)
+  kubectl patch hdfs/<CLUSTER_NAME> --subresource=status --type=merge \
+    --patch '{"status": {"deployedProductVersion": "<NEW_VERSION>"}}'
+  ```
 
-```shell
-hdfs dfsadmin -rollingUpgrade finalize
-```
-
-#### Update the deployed product version status
-
-```shell
-kubectl patch hdfs/<CLUSTER_NAME> --subresource=status --type=merge \
-  --patch '{"status": {"deployedProductVersion": "<NEW_VERSION>"}}'
-```
+</details>

.markdownlint.yaml

@@ -18,3 +18,9 @@ MD013:
 MD024:
   # Only check sibling headings
   siblings_only: true
+
+# MD033 - no-inline-html
+MD033:
+  allowed_elements:
+    - details
+    - summary