Allow injecting custom feeddata instead of default data

[bravecobra]

We need a way to overwrite the seeddata and the configuration with whatever files the user wants to provide.
And we'll use the default ones if nothing is provided to seed.
We also want the flag of the seeding to be able to be set.

Helm can not get the content of an external file directly: helm/helm#3276
We can get the content of an external file like the following. The encoding and decoding is to solve the newline problem

So if we deploy like this:

helm install --set-file adminAppSettingsValues=./admin-appsettings.json

We can then apply that in the Chart like

apiVersion: v1
kind: ConfigMap
metadata:
  name: <config-name>
data:
  appsettings.json: |-
  {{ .Values.adminAppSettingsValues}}`

and the based on the existence of .Values.adminAppSettingsValues, start the seeding from that content. We need to do that for each of the json files to allow overriding externally.