[Demo with Importer] Add new flag for Flux controllers

[rytswd]

Change Overview

This adds a dummy flag of --new-common-flag for all the Flux controllers. This uses Importer template, and each controller has a dedicated YAML file.

Importer Details

You can find more in #5

Setup Details

Service Based Configuration

I have broken up the Flux installation spec into several files based on services.

importer generate and .gitattributes

With importer generate command, you can use Importer to create a separate file rather than updating the file in place. The generated file only would only have changes defined in the imported files, and thus you could introduce .gitattributes file to mark that the file is auto-generated.

This repository has .gitattributes defining that *.gen.yaml would be considered as a generated file, and thus you will see the note Some generated files are not rendered by default in the diff view.