Support running kubernetes from OpenShift template

[aweiteka]

Extend kubernetes provider so it could run an unaltered OpenShift template via inherit.

...
  - artifacts: 
      openshift: 
        - file:path/to/template.json
      kubernetes:
        inherit: openshift
...

[vpavlin]

This is a bit problematic - we can do that for simple templates like [1], but it would mean to reimplement generators [2].

Michal Fojtik suggested to use openshift running in Docker container and doing a call like:

cat foo.template | sudo docker exec -it openshift-origin bash -c "osc process -f -"

if osc is not available.

[1] https://github.com/openshift/origin/blob/master/examples/zookeeper/template.json#L362
[2] https://github.com/openshift/origin/blob/master/examples/sample-app/application-template-stibuild.json#L407
[3] https://github.com/openshift/origin/blob/master/pkg/template/generator/expressionvalue.go

[aweiteka]

Thoughts/summary:

• We should define generator functions in the Nulecule spec. Not sure how that would be implemented but here's an issue: Add support for dynamic functions nulecule#97
• We cannot use osc CLI without an OpenShift server. This defeats the purpose of app portability.
• I think we should support basic openshift templates for now basically pulling out any kube content. It's not clear which params should be exposed since they're in the Nulecule file and openshift template. Using this example template kubectl create ... any data structure that is of "Kind" DeploymentConfig and Service.

[aweiteka]

@goern is this part of our CDK GA milestone story? I vote 'no' since we have not pulled this in as a primary user story.

[goern]

I see some feature misfit for that, referring to vpavlins comment and dont really see that this is part of the story...

[goern]

prerequisite: an OpenShift environment that is capable of processing the template inherited with the Atomic App.