Implement the functionality to set the flags via environment variables

[tiwalter]

Purpose of the feature (why)

I use this addon in a Docker environment and have to adjust some settings (listen-address, etc.). Therefore, the k8s config file has to be modified. This is a manual overhead and leads to duplicate config files (one for the host and one for the Docker environment).

Your idea (how)

It would be very helpful if the user could set the flags additionally via environment variables. Libs like "viper" (https://github.com/spf13/viper) can ensure this functionality. The flags always should have higher priority than the env var, if both are set.

With this feature, you can adjust the settings without modifying the k8s config file.

[vrabbi]

This would be extremely beneficial for the password grant flow as well to allow non interactive login with the user password in env vars instead of hardcoded in the kubeconfig