Create an option for defining the user in home-manager modules

This will replace existing per-module user configuration.

Or, rather, it already did for git.

modules/home/base.nix

@@ -0,0 +1,10 @@
+{ config, configFiles, lib, pkgs, ... }:
+
+with lib;
+
+{
+	options.myModules.home.user = mkOption {
+		description = "The username of the user for building paths";
+		type = types.str;
+	};
+}

modules/home/default.nix

@@ -1,5 +1,6 @@
 {
 	imports = [
+		./base.nix
 		./fish.nix
 		./git.nix
 		./neovim.nix