Initializes a user's home directory, but as an initContainer, rather than as something controlled by Moneypenny.
This container will run with the same environment and volume mounts as the notebook container--however, it will run with privilege.
It will consult the JUPYTERHUB_USER, EXTERNAL_UID, and
EXTERNAL_GID environment variables, and then construct a home
directory for the named user with that UID/GID pair, and set it to mode
0700.
This obviously requires that the NFS server on the far end be mounted
no_root_squash or the moral equivalent, if a different distributed
filesystem is used.
This is simply a busybox image with an additional shell script to check that the environment variables are present and that the directory, if already present, is correctly owned. The init container will warn if the mode is not 0700, but will not consider that an error.