fnott: refactor module

- Change generation behavior to always generate a configuration file
  and pass it explicitly to fnott, it enforces the module to be
  hermetic instead of offloading the configuration selection to
  heuristics.
- Various style changes.
- Fix issue where fnott would abort due to an invalid config file when
  both the configFile and settings options are unset.
- Remove the empty-settings test as a configuration file is now
  already generated.

Suggested-by: Robert Helgesson <robert@rycee.net>

tests/modules/services/fnott/default.nix

@@ -1,5 +1,4 @@
 {
-  fnott-empty-settings = ./empty-settings.nix;
   fnott-example-settings = ./example-settings.nix;
   fnott-global-properties = ./global-properties.nix;
   fnott-systemd-user-service = ./systemd-user-service.nix;

tests/modules/services/fnott/empty-settings.nix

@@ -1,15 +0,0 @@
-{ config, lib, pkgs, ... }:
-
-{
-  config = {
-    services.fnott = {
-      enable = true;
-      package = pkgs.writeScriptBin "dummy-fnott" "";
-      settings = { };
-    };
-
-    nmt.script = ''
-      assertPathNotExists home-files/.config/fnott
-    '';
-  };
-}

tests/modules/services/fnott/systemd-user-service-expected.service

@@ -1,6 +1,6 @@
 [Service]
 BusName=org.freedesktop.Notifications
-ExecStart=@fnott@/bin/fnott -c /home/hm-user/.config/fnott/fnott.ini
+ExecStart=@fnott@/bin/fnott -c '/home/hm-user/.config/fnott/fnott.ini'
 Type=dbus
 
 [Unit]

tests/modules/services/fnott/systemd-user-service.nix

@@ -8,8 +8,6 @@
     };
 
     nmt.script = ''
-      assertPathNotExists home-files/.config/fnott/fnott.ini
-
       assertFileContent \
         home-files/.config/systemd/user/fnott.service \
         ${./systemd-user-service-expected.service}