root|modules: update flake.lock, fix systemd messing with machine-id …

…early

In the newest release of systemd (or the _newer_ release compared to the previous nixpkgs revision), a new `systemd-machine-id-commit.service` was introduced to help ensure `/etc/machine-id` was correctly saved from a transient fs like `tmpfs` to a real persistent device. This is for fairly obvious reasons, systemd relies on the machine-id to store logs and other system stateful information, and losing it each time defuncts those data.

Unfortunately, whilst well intentioned this service does nothing for my use-case because we already handle this ourselves (ignoring the `nixos-install` issue which has yet to be fixed). As a result, we can simply disable this service since there is enough assurance it won't be needed. Checking `systemctl --failed` shows no other services failing due to this change, which gives me the confidence in knowing this service is non-essential to anything else, and can be safely disabled.

modules/common/persist/module-impl.nix

@@ -41,11 +41,16 @@ in {
       mode = "700";
     }];
 
-    # Ensure consistency with some systemd tools.
+    # machine-id is widely used by systemd to track system-specific
+    # things, very important to persist it for general expectations.
     my.persist.files = [
       "/etc/machine-id"
     ];
 
+    # Kill the systemd-machine-id-commit.service from systemd 256.7,
+    # it does what we already handle via the activation script.
+    systemd.services."systemd-machine-id-commit".enable = false;
+
     system.activationScripts.persist = lib.stringAfter [ "users" "groups" ] ''
       log() {
         echo "[persist] $1"