Refactor Nulecule params

[rtnpro]

Refactor Nulecule/atomicapp params to support developing nested Nulecule applications easy. This work is to fix the issues discussed in projectatomic/nulecule#187

Fixes #423.

[rtnpro]

@kanarip @dustymabe @vpavlin @cdrage
You can try out this code with projectatomic/nulecule-library#30

[cdrage]

@rtnpro a lot of tests fail, we'll have to have compatibility from putting params both under graph and params, unless our spec changes in the future

[dustymabe]

I have not looked at the code at all but have looked at the POC code in projectatomic/nulecule-library#30. This looks interesting and I am going through and going to try to convert my etherpad app to do the same thing and see what all I need to change.

@cdrage. Do you mind looking at this in detail and also consider the work you did for xpathing when you review? Start with projectatomic/nulecule-library#30 and then we can both look at the code in this PR.

[dustymabe]

One thing I noticed when playing around with this is that only parts of the config are getting passed to the provider. An example is that if I put 'providerconfig' into the answers.conf file it does not make it into the provider code. The logger.debug("Given config: %s", self.config) from the kubernetes provider is a good one to look at to see what is getting passed.

[rtnpro]

@vpavlin @dustymabe @cdrage @kadel @goern

So, I updated the POC for refactoring params in Nulecule spec here:
rtnpro/nulecule-library@4c9ee7b

It allows:

Cross referencing params

This allows referencing params definition across sibling components in a Nulecule. It fixes duplicate param problem in answers or config data.

Config mapping

It allows channelize config from current Nulecule to its external Nulecule children, or, local component according to their needs. This allows, optionally, in controlling access to config data to external Nulecule apps.

The end result will be a cleaner and understandable answers file, where users enter
param values only for the immediate Nulecule they are consuming.

However, this will not take the freedom of overriding config data for a Nulecule component at any level in the Nulecule tree by adding a section for it in answers file, just like the way it works now.

[dustymabe]

@rtnpro I looked at your sentry example and it seems like there is a lot of mixing of ideas in there, which is probably a mistake. Do you mind adding your new proposal to https://gist.github.com/rtnpro/17add2ab248ac34a7687 so it can clearly be evaluated?

[cdrage]

Woo! projectatomic/nulecule#196 has been merged, no more blockers @rtnpro

[rtnpro]

@dustymabe @cdrage @surajssd @containscafeine
Let's resume discussions on this and reach a decision ASAP.

https://gist.github.com/rtnpro/17add2ab248ac34a7687#file-nulecule_with_param_cross_ref_and__optional_mapping-md