Argo-cd: Environment styling

[barryoneill]

It would be really nice if the UI has some configuration options offering some rudimentary style overrides, to make it clearer to a user who may have access to dev _and_ production argocd deployments.

Eg, for production, some text could be added to the header, and perhaps some colors could be overridden:

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[barryoneill]

Pinging to keep alive, in the case I get a chance to contribute this fix.

[alexec]

If you'd like to contribute, this should help you:

https://argoproj.github.io/argo-cd/developer-guide/

[AndiDog]

How fine-grained should the customization be? My first idea would be to override the page element's background, e.g. using a transparent PNG. Here's a contrived example:

That could read "production" or "dev".

Configuration-wise, this could be done with a new parameter like argocd-server [default params like --staticassets /shared/app ...] --extracss /my/mounted/config/map/files/style-production.css and users configure the CSS files inside a config map (1MB limit should suffice).