chore: Add demo upgrade issue template

Author: Techassi

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

@@ -0,0 +1,115 @@
+---
+name: Pre-Release Demo Upgrade Testing from Stable to Nightly
+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 demos on nightly versions"
+labels: ['epic']
+assignees: ''
+---
+
+<!--
+    Make sure to update the link in '.github/ISSUE_TEMPLATE/release.md' when
+    you change the filename.
+-->
+
+<!--
+    DO NOT REMOVE THIS COMMENT. It is intended for people who might copy/paste from the previous release issue.
+    This was created by an issue template: https://github.com/stackabletech/issues/issues/new/choose.
+-->
+
+## Pre-Release Demo Testing on Nightly
+
+Part of <https://github.com/stackabletech/issues/issues/TRACKING_ISSUE>
+
+This is testing:
+
+1. The demos documented in nightly (with the updated product versions) still work.
+2. That the operators can be upgraded from the current release to the nightly release and do not
+   negatively impact the products.
+
+> [!NOTE]
+> Record any issues or anomalies during the process in a comment on this issue.
+> Eg:
+>
+> ```plain
+> :green_circle: **airflow-scheduled-job**
+>
+> The CRD had been updated and I needed to change the following in the manifest:
+> ...
+> ```
+
+Replace the items in the task lists below with the applicable Pull Requests (if any).
+
+<!--
+    The following list was generated by:
+
+    # go to the demos repository, then run:
+    yq '.demos | keys' demos/demos-v2.yaml \
+    | sed -e 's/- //g' \
+    | sort \
+    | xargs -I {} echo "- [ ] [{}](https://docs.stackable.tech/home/nightly/demos/{})"
+-->
+
+```[tasklist]
+### Testing Demos on Nightly
+- [ ] [airflow-scheduled-job](https://docs.stackable.tech/home/nightly/demos/airflow-scheduled-job)
+- [ ] [data-lakehouse-iceberg-trino-spark](https://docs.stackable.tech/home/nightly/demos/data-lakehouse-iceberg-trino-spark)
+- [ ] [end-to-end-security](https://docs.stackable.tech/home/nightly/demos/end-to-end-security)
+- [ ] [hbase-hdfs-load-cycling-data](https://docs.stackable.tech/home/nightly/demos/hbase-hdfs-load-cycling-data)
+- [ ] [jupyterhub-pyspark-hdfs-anomaly-detection-taxi-data](https://docs.stackable.tech/home/nightly/demos/jupyterhub-pyspark-hdfs-anomaly-detection-taxi-data)
+- [ ] [logging](https://docs.stackable.tech/home/nightly/demos/logging)
+- [ ] [nifi-kafka-druid-earthquake-data](https://docs.stackable.tech/home/nightly/demos/nifi-kafka-druid-earthquake-data)
+- [ ] [nifi-kafka-druid-water-level-data](https://docs.stackable.tech/home/nightly/demos/nifi-kafka-druid-water-level-data)
+- [ ] [signal-processing](https://docs.stackable.tech/home/nightly/demos/signal-processing)
+- [ ] [spark-k8s-anomaly-detection-taxi-data](https://docs.stackable.tech/home/nightly/demos/spark-k8s-anomaly-detection-taxi-data)
+- [ ] [trino-iceberg](https://docs.stackable.tech/home/nightly/demos/trino-iceberg)
+- [ ] [trino-taxi-data](https://docs.stackable.tech/home/nightly/demos/trino-taxi-data)
+```
+
+### Testing Instructions
+
+These instructions are for deploying the nightly demo, as well as upgrading the operators and CRDS.
+
+```shell
+# Install demo (stable operators)
+stackablectl demo install <DEMO_NAME>
+
+# --- IMPORTANT ---
+# Run through the nightly demo instructions (refer to the tasklist below).
+
+# Get a list of installed operators
+stackablectl operator installed --output=plain
+
+# --- OPTIONAL ---
+# Sometimes it is necessary to upgrade Helm charts. Look for other Helm Charts
+# which might need updating.
+
+# First, see which charts are installed. You can ignore the stackable-operator
+# charts, or anything that might have been installed outside of this demo.
+helm list
+
+# Next, add the applicable Helm Chart repositories. For example:
+helm repo add minio https://charts.min.io/
+helm repo add bitnami https://charts.bitnami.com/bitnami
+
+# Finally, upgrade the Charts. For example:
+helm upgrade minio minio/minio --version x.x.x
+helm upgrade postgresql-hive bitnami/postgresql --version x.x.x
+# --- OPTIONAL END ---
+
+# Uninstall operators
+stackablectl release uninstall <CURRENT_RELEASE>
+
+# Update CRDs to nightly version (on main)
+# Repeat this for every operator used by the demo
+kubectl replace -f https://raw.githubusercontent.com/stackabletech/commons-operator/main/deploy/helm/commons-operator/crds/crds.yaml
+kubectl replace -f https://raw.githubusercontent.com/stackabletech/...-operator/main/deploy/helm/...-operator/crds/crds.yaml
+
+# Install nightly version of operators (use the list from the earlier step
+# before deleting the operators)
+stackablectl operator install commons ...
+
+# Optionally update the product versions in the CRDs, e.g.:
+kubectl patch hbaseclusters/hbase --type='json' -p='[{"op": "replace", "path": "/spec/image/productVersion", "value":"x.x.x"}]' # changed
+```