I want to have one configuration that I can build for different users, i.e. the user name, group etc. should be specific to that one build. I don’t want to use home-manager for custom configs, everyone will get the same system, except for their user name.
That would be possible, but I would love to have everything in source control and deploy through a Gitlab pipeline. So adding a user would go through our usual approval process and be documented accordingly.
Generally when you need multiple configurations that are the same except for some details, you create a common module, and then give each system its own configuration.nix that imports the common module and also sets the system-specific details