feat: Airflow with Event-scheduling, Triggerer, Opa

[adwk67]

Fixes #223
Requires stackabletech/docker-images#1313

N.B. to test before merging switch these links to local ones and call the demo with -s and -d pointing to local files:

• https://www.github.com/stackabletech/demos/pull/320/files#diff-30a11a28ac0e300f6d36031e23551109b4f292f79cd1921572cd78636aaf9f76R49-R54
• https://www.github.com/stackabletech/demos/pull/320/files#diff-54b42f19e6c5a8380e1d86d888d98cdf397e3763c2138284b528660343a71dd0R149-R152

e.g. stackablectl demo install airflow-scheduled-job -s stacks/stacks-v2.yaml -d demos/demos-v2.yaml -n airflow-demo

Demo tested on Kind using LoadBalancer provided by https://github.com/kubernetes-sigs/cloud-provider-kind.

[dervoeti]

Great demo! Worked fine for me.
Approving this already because my remarks are just nit picking.

Found one more nit:
The docs say in the last step that patches the Airflow cluster "To include this in the list of DAGs (without removing the existing ones) ...", but the patch actually removes the existing ones. Or maybe I misunderstand it.
So I'd either remove the part in brackets or add the other volume mounts to the patched Airflow resource.

[adwk67]

Great demo! Worked fine for me. Approving this already because my remarks are just nit picking.

Found one more nit: The docs say in the last step that patches the Airflow cluster "To include this in the list of DAGs (without removing the existing ones) ...", but the patch actually removes the existing ones. Or maybe I misunderstand it. So I'd either remove the part in brackets or add the other volume mounts to the patched Airflow resource.

Thanks! Have fixed that here: 7503715