Motivation for this change

fix for #29922

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • [ X] NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested with the following configuration:

{ config, pkgs, ... }:

{
	services.gogs = {
		enable = true;

		user = "git";
		group = "git";

		domain ="git.example.com";
		rootUrl = "https://git.example.com/";

		database.path = "/data/git/data/gogs.db";
		repositoryRoot = "/data/git/repositories";
		stateDir = "/data/git/";
	};

	users.users.git = {
		isSystemUser = true;
		group = "git";
		shell = pkgs.bash;
		home = "/data/git";
	};
	users.groups.git = {};
}

• Fits CONTRIBUTING.md.

Edit: fixed typo in example configuration