Add CLI flag to replicate user pod (volumes, image, etc.) settings in job pod

[Adam-D-Lewis]

It'd be nice for users to have a way to replicate their user pod in the job pod so they could access all their data similarly to how they would if they were running in their Jupyterhub user pod. I'd propose the addition of a --replicateUserPod flag which would cause the initContainers, volumes, volumeMounts, and image of the user pod to be added to the job pod. This might be implemented in the following way:

• user submits job kbatch submit job --replicateUserPod ...
• then kbatch client looks for socket.gethostname() to find what pod we're in, and passes hostname to kbatch-proxy
• kbatch-proxy calls kubernetes.client.CoreV1Api().read_namespaced_pod(hostname, namespace) to get pod spec
  • pulls out initContainers, volumes, volumeMounts, image and add these to spec of job pod to be submitted
• kbatch-proxy submits job otherwise the same as it does currently