Containerize the frontend web VM scale set

[hosungsmsft]

We'd like to containerize at least the frontend web VM scale set, if not the entire cluster. Kubernetes is considered a viable orchestrator, but it's uncertain how app containers may be deployed using ARM templates, so need investigation on that.

We also learned recently that Catalyst IT EU presented their Moodle containerization experiences in MoodleMoot UK/Ireland 2018 (search for "containerisation" after clicking the link), and it'd be great if we can learn and improve from their experiences.

Initially setting the milestone as v1.5.1 for planning, but it's well understood that this work might take longer, in which case the milestone will be adjusted accordingly.

[hosungsmsft]

Done some preliminary research from our side. Identified 2 points that may affect the timeline of this issue:

• AKS (managed K8s on Azure, which is our preferred choice, instead of the K8s option on the original ACS) is not yet GA, available only in select regions. To reduce false hope, we'll probably need to wait for AKS to be GA.
• Custom VNET support on AKS is not available, and yet we need it to mount the remote volume on the NFS or the Gluster server. Ultimately we'd like those file servers as containers, but it doesn't appear to be viable in the near future, so we need our web containers to be able to access the file servers on VM(s).

For these matters, this change might need to be delayed until AKS GA. I'm adjusting the priority as such, and we'll discuss what milestone this should belong to in our meeting.

[hosungsmsft]

#78 is for the generic research/recommendations of architecture for containerization that possibly combines hosting multiple Moodle sites in a single cluster.

[hosungsmsft]

This issue is put on hold for now as per our phone call discussion. Dropping the milestone.