Document lifecycle management of Azure persistent volumes

[wisack]

We want to be able to have persistent storage for e.g. database (MongoDB and InfluxDB).

Helm charts that deploy MongoDB and InfluxDB can create their persistent volumes during deployment.
By default persistent volumes created by the deployment charts are destoyed when service deployments are deleted from K8S cluster.
Deployment could be configured in such a way that created persistent volumes are NOT destroyed when service deployments of MongoDB and InfluxDB are deleted from K8S cluster.

Document how to

1. Create persistent volumes that are not destroyed when service deployments are deleted from K8S
2. Use the existing persistent volumes when service deployments are created.

Optionally persistent volumes could be created manually before service deployments.

Check work done in smaddis/smad-deploy-azure#38 and #30 before starting this, since AKS can create Persistent volumes to Azure storage automatically based on PersistentVolumeClaims in Helm charts.

More info on Azure storage is available for example here:
https://docs.microsoft.com/en-us/azure/aks/concepts-storage

There might be a need to create Azure persistent volume (storage) for e.g. database manually before the database is deployed to K8S / AKS.

~~This ticket is about ~~
1. investigating how one attached already created Azure storage to Pods created by a Helm chart.
2. investigating and designing how manual provisioning / creation and lifecycle management of storage should be done in Azure