use getenv in configs

How to use GitHub

• Please use the 👍 reaction to show that you are interested into the same feature.
• Please don't comment if you have no relevant information to add. It's just extra noise for everyone subscribed to this issue.
• Subscribe to receive notifications on status change and new comments.

Is your feature request related to a problem? Please describe.

Simply put, I can understand using the environment variables for initialising NC, but then not using environment variables for continued operations seems silly to me. Why hardcode the values when they are initially read from environment variables anyway?
Additionally using environment variables instead of hardcoding would allow using container secrets directly.
Additionally rotating DB passwords or locations becomes a breeze since it would all be done through environment variables.

Describe the solution you'd like

Star using: 'var' => getenv('ENV_VAR') as much as possible since manually editing config.php can be done eitherway.

Describe alternatives you've considered

Doing it myself, while yes I've done this. I see that this would be likely to benefit other people as well.

Additional context

Since this is an "advanced" image when compared to AIO I can understand potential hesitancy to adopt my suggestions. Yet I believe that it will help since it doesn't detract from original deployment methods in any way.

Start by locating the Docker image configuration and the existing environment-variable initialization that writes values into config.php. Identify which continued-operation settings are still hardcoded and assess whether getenv can safely supply them, including container-secret and rotation cases. Done means the relevant settings consistently read environment variables without removing manual config.php support.