Kubeflow ROCKs

Collection of ROCKs for Kubeflow components.

Development notes

Rockcraft tutorial: https://canonical-rockcraft.readthedocs-hosted.com/en/latest/tutorials.html
Example: https://github.com/jnsgruk/seldon-core-operator-rock
Use stage-packages to install required packages for application to run.
Use build-environment to setup environment variables for build stage.
Use build-packages and build-snaps for build stage. Those will not be used by application. As a result, if build and application require the same package, it needs to be in both build-packages and stage-packages
If issues with LXD/Docker arise review firewall setup: https://linuxcontainers.org/lxd/docs/master/howto/network_bridge_firewalld/
While building ROCKs these commands are very helpful:
```
rockcraft clean
lxc --project rockcraft image list
```
Entry point in ROCK is Pebble. At this point there is no way to specify other entry point. To start container, a Pebble layer is added via adding 001-deafault.yaml file to /var/lib/pebble/default/layers/. Refer to source code for more details.

To build ROCK images for Kubeflow components:

cd <image-directory>
rockcraft pack