nixos/ntfy-sh: clean up DynamicUser workarounds

this commit removes the static assignments for the ntfy-sh user and
group. furthermore, it removes some tmpfiles.d rules which where
initially put in place by https://github.com/NixOS/nixpkgs/pull/234811.
these are however not required, as ntfy-sh will automatically create the
required files and systemd automatically handles the migration process.

A nixosTest is added to demonstrate that the migration is working
reliably.

This also fixes an issue with where systemd would sometimes not start
ntfy-sh. The tmpfiles rules in combination with impermanence caused `/
var/lib/ntfy-sh` to be a directory when it should have been a symlink.

nixos/modules/services/misc/ntfy-sh.nix

@@ -84,12 +84,6 @@ in
         cache-file = mkDefault "/var/lib/ntfy-sh/cache-file.db";
       };
 
-      systemd.tmpfiles.rules = [
-        "f ${cfg.settings.auth-file} 0600 ${cfg.user} ${cfg.group} - -"
-        "d ${cfg.settings.attachment-cache-dir} 0700 ${cfg.user} ${cfg.group} - -"
-        "f ${cfg.settings.cache-file} 0600 ${cfg.user} ${cfg.group} - -"
-      ];
-
       systemd.services.ntfy-sh = {
         description = "Push notifications server";
 

nixos/tests/all-tests.nix

@@ -559,6 +559,7 @@ in {
   nscd = handleTest ./nscd.nix {};
   nsd = handleTest ./nsd.nix {};
   ntfy-sh = handleTest ./ntfy-sh.nix {};
+  ntfy-sh-migration = handleTest ./ntfy-sh-migration.nix {};
   nzbget = handleTest ./nzbget.nix {};
   nzbhydra2 = handleTest ./nzbhydra2.nix {};
   oh-my-zsh = handleTest ./oh-my-zsh.nix {};

nixos/tests/ntfy-sh-migration.nix

@@ -0,0 +1,77 @@
+# the ntfy-sh module was switching to DynamicUser=true. this test assures that
+# the migration does not break existing setups.
+#
+# this test works doing a migration and asserting ntfy-sh runs properly. first,
+# ntfy-sh is configured to use a static user and group. then ntfy-sh is
+# started and tested. after that, ntfy-sh is shut down and a systemd drop
+# in configuration file is used to upate the service configuration to use
+# DynamicUser=true. then the ntfy-sh is started again and tested.
+
+import ./make-test-python.nix {
+  name = "ntfy-sh";
+
+  nodes.machine = {
+    lib,
+    pkgs,
+    ...
+  }: {
+    environment.etc."ntfy-sh-dynamic-user.conf".text = ''
+      [Service]
+      Group=new-ntfy-sh
+      User=new-ntfy-sh
+      DynamicUser=true
+    '';
+
+    services.ntfy-sh.enable = true;
+    services.ntfy-sh.settings.base-url = "http://localhost:2586";
+
+    systemd.services.ntfy-sh.serviceConfig = {
+      DynamicUser = lib.mkForce false;
+      ExecStartPre = [
+        "${pkgs.coreutils}/bin/id"
+        "${pkgs.coreutils}/bin/ls -lahd /var/lib/ntfy-sh/"
+        "${pkgs.coreutils}/bin/ls -lah /var/lib/ntfy-sh/"
+      ];
+      Group = lib.mkForce "old-ntfy-sh";
+      User = lib.mkForce "old-ntfy-sh";
+    };
+
+    users.users.old-ntfy-sh = {
+      isSystemUser = true;
+      group = "old-ntfy-sh";
+    };
+
+    users.groups.old-ntfy-sh = {};
+  };
+
+  testScript = ''
+    import json
+
+    msg = "Test notification"
+
+    def test_ntfysh():
+      machine.wait_for_unit("ntfy-sh.service")
+      machine.wait_for_open_port(2586)
+
+      machine.succeed(f"curl -d '{msg}' localhost:2586/test")
+
+      text = machine.succeed("curl -s localhost:2586/test/json?poll=1")
+      for line in text.splitlines():
+        notif = json.loads(line)
+        assert msg == notif["message"], "Wrong message"
+
+      machine.succeed("ntfy user list")
+
+    machine.wait_for_unit("multi-user.target")
+
+    test_ntfysh()
+
+    machine.succeed("systemctl stop ntfy-sh.service")
+    machine.succeed("mkdir -p /run/systemd/system/ntfy-sh.service.d")
+    machine.succeed("cp /etc/ntfy-sh-dynamic-user.conf /run/systemd/system/ntfy-sh.service.d/dynamic-user.conf")
+    machine.succeed("systemctl daemon-reload")
+    machine.succeed("systemctl start ntfy-sh.service")
+
+    test_ntfysh()
+  '';
+}