Support merging (json) values from two configmap keys

[simonkotwicz]

Is your feature request related to a problem? Please describe.
We are trying to simplify our deployment files and configmaps. Right now they are very messy due to the fact that we are trying to merge multiple configmap values that are in the form of stringified json values. Because this is not natively supported we end up with very messy workarounds.

Describe the solution you'd like
Support merging (json) values from two configmap keys, something like:

  env:
    - name: my-service
      valueFrom:
        configMapKeyRef:
          name: default
          key: my-service
          type: json
    - name: my-service
      overrideStrategy: merge # default would be replace
      valueFrom:
        configMapKeyRef:
          name: overrides
          key: my-service
          type: json

or

  envFrom:
  - configMapKeyRef:
      name: default
      key: my-service
  - configMapKeyRef:
      name: overrides
      key: my-service

Describe alternatives you've considered
Alternatives include:

• using envFrom and both splitting up our configmaps as well as flattening them out (to remove stringified json values) so that we can leverage the merging that is currently supported with envFrom

[alewitt2]

#290 is almost done and i will get a release out for it today. I also when ahead and added some extra handlebar helpers that i think you may need as you start to pull in and merge json data and try to write them back out to configmaps. Thats just a gut feeling though, if you dont use them, no worries

[alewitt2]

version 0.16.0 is released