Adding support for EmptyDir volumes to kubernetes executor

It would be interesting to have support for EmptyDir volume type in kubernetes executor, especially with support of the "Medium" field that can be either set to "" (Empty string) which would provide a volume on whatever the node provides, or to "Memory" which would provides a tmpfs. (https://kubernetes.io/docs/concepts/storage/volumes/#emptydir)

This can be very useful when you're building using services such as databases, that are provisionned, populated, tested against and deleted at every build. This can enhance drastically the build time.

This issue is a follow-up to https://gitlab.com/gitlab-org/gitlab-runner/issues/2258,

mentioned in issue #2258 (closed)

added executorkubernetes feature proposal labels

mentioned in merge request !660 (merged)

I think the first pass on this should just get basic emptyDir working without worrying about a "Medium" field.

The "Medium" field is just a field forwarded to the k8s API, there's nothing complicated about it, that's why i do not see the point in splitting this.

Btw just having regular emptyDir might not be what suits most people use-cases, as many woudld want "Memory" emptyDir, which ones are tmpfs in reality.

changed the description

closed via merge request !660 (merged)