Improve Airflow deployment

[c0c0n3]

#9 made a first stab at Airflow deployment. We should improve on that by implementing

• Integration into Argo CD GitOps pipeline.
• Istio routing to expose the Web UI to clients outside the cluster.

Also we should check out the community chart again and see if we can get it to work since it looks better than the official chart. Finally, when done, don't forget to clean up the deployment/plat-infra-services/airflow directory :-)