ENV and Java Props substitution while reading file

[jkroepke]

It's just an idea. Vote: 👍 if you think this feature is useful. Then I'll investigative into it.

Is your feature request related to a problem? Please describe.
Handling multiple environments needs multiple json files each environment

Describe the solution you'd like
keycloak-config-cli should support a substitution of the json files.

Describe alternatives you've considered
multiple json files each environment

Additional context
FasterXML/jackson-dataformats-text#28

I would like to use a native/jackson way instead a new dependency if possible.