Use a persistent volume as storage for the Ansible Control Host container

[alicel]

Currently, all the the Ansible automation files are stored within the container file system, including the configuration files through which users specify the values of all required ZDM variables plus any optional ones that they may wish to explicitly set.

This means that, if the Ansible Control Host container needs to be recreated for whatever reason, the configuration files populated by the user are currently lost. This does not happen often, but when it does it is a suboptimal experience for the user. It may also become a more likely scenario to some extent after https://datastax.jira.com/browse/ZDM-573.

To improve this we should create a persistent volume when the ACH container is first created, and attach this volume to the container. All files should be stored on this volume.

If the ACH container is recreated, the existing volume should just be reattached to it and the files could still be used as they are in the new container (unless the new container used a version of the automation that contained breaking changes, in which case the files would have to be adapted, but this would be rare and very unlikely in practice). This flow should be handled by the ZDM Utility (similarly to what it is already doing when it finds an existing ACH container).

This ticket is part of the second (longer-term) set of changes to improve the ZDM Versioning and support version-based documentation.

┆Issue is synchronized with this Jira Task by Unito
┆Components: Automation
┆Priority: Major