Add a role for flatpak.

nix/configuration/roles/flatpak/default.nix

@@ -0,0 +1,62 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+{
+  imports = [ ];
+
+  options.me = {
+    flatpak.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to install flatpak.";
+    };
+  };
+
+  config = lib.mkIf config.me.flatpak.enable {
+    services.flatpak.enable = true;
+
+    environment.persistence."/persist" = lib.mkIf (config.me.mountPersistence) {
+      hideMounts = true;
+
+      directories = [
+        {
+          directory = "/var/lib/flatpak";
+          user = "root";
+          group = "root";
+          mode = "0755";
+        }
+      ];
+
+      users.talexander = {
+        directories = [
+          {
+            # User-specific configuration.
+            directory = ".local/share/flatpak";
+            user = "talexander";
+            group = "talexander";
+            mode = "0755";
+          }
+          {
+            # App data
+            directory = ".var/app";
+            user = "talexander";
+            group = "talexander";
+            mode = "0755";
+          }
+          {
+            # Flatpak Lutris installs
+            directory = "Games";
+            user = "talexander";
+            group = "talexander";
+            mode = "0755";
+          }
+        ];
+      };
+    };
+  };
+}