WIP home/borgmatic: correctly deduce system hostname from os config

Also add some TODOs for future me :^)

modules/services/borgmatic.nix

@@ -1,19 +1,23 @@
 {
   flake.modules.homeManager.borgmatic =
     { config
+    , osConfig
     , pkgs
+    , lib
     , ...
     }:
     let
-      hostname = config.networking.hostname;
+      hostname = osConfig.networking.hostName;
       username = config.home.username;
     in
     {
       home.packages = with pkgs; [
         libnotify
+        borgmatic
       ];
 
       programs.borgmatic = {
+        enable = true;
         backups.default = {
           location = {
             repositories = [
@@ -25,6 +29,7 @@
             excludeHomeManagerSymlinks = true;
             patterns = [
               #TODO: home.homeDirectory might be usable here
+              #TODO: should be user and machine specific
               "R /home/${username}/Documents"
               "R /home/${username}/.ssh"
               "- /home/${username}/Documents/SteamLibrary"
@@ -50,6 +55,8 @@
         };
       };
 
+      #TODO: there is a services.borgmatic
+
       systemd.user.services.borgmatic = {
         Unit.Description = "Create a backup using borgmatic";
         Service.ExecStart = "${pkgs.borgmatic}/bin/borgmatic create --stats";