nixos/ifm: replace activation script with systemd tmpfiles

See https://github.com/NixOS/nixpkgs/issues/475305

nixos/modules/services/web-apps/ifm.nix

@@ -53,6 +53,7 @@ in
       description = "Improved file manager, a single-file web based filemanager";
 
       after = [ "network-online.target" ];
+      wants = [ "network-online.target" ];
       wantedBy = [ "multi-user.target" ];
 
       environment = {

nixos/tests/ifm.nix

@@ -7,30 +7,42 @@
   };
 
   nodes = {
-    server = rec {
-      services.ifm = {
-        enable = true;
-        port = 9001;
-        dataDir = "/data";
-      };
+    server =
+      { config, ... }:
+      {
+        services.ifm = {
+          enable = true;
+          port = 9001;
+          dataDir = "/data";
+        };
 
-      system.activationScripts.ifm-setup-dir = ''
-        mkdir -p ${services.ifm.dataDir}
-        chmod u+w,g+w,o+w ${services.ifm.dataDir}
-      '';
-    };
+        systemd.tmpfiles.settings = {
+          ifm-data-dir = {
+            ${config.services.ifm.dataDir}.d = {
+              mode = "0777";
+              user = "root";
+              group = "root";
+            };
+          };
+        };
+      };
   };
 
-  testScript = ''
-    start_all()
-    server.wait_for_unit("ifm.service")
-    server.wait_for_open_port(9001)
-    server.succeed("curl --fail http://localhost:9001")
+  testScript =
+    # python
+    ''
+      start_all()
+      server.wait_for_unit("ifm.service")
+      server.wait_for_open_port(9001)
+      server.succeed("curl --fail http://localhost:9001")
 
-    server.succeed("echo \"testfile\" > testfile && shasum testfile >> checksums")
-    server.succeed("curl --fail http://localhost:9001 -X POST -F \"api=upload\" -F \"dir=\" -F \"file=@testfile\" | grep \"OK\"");
-    server.succeed("rm testfile")
-    server.succeed("curl --fail http://localhost:9001 -X POST -F \"api=download\" -F \"filename=testfile\" -F \"dir=\" --output testfile");
-    server.succeed("shasum testfile >> checksums && shasum --check checksums")
-  '';
+      server.succeed('echo "testfile" > testfile')
+      server.succeed("shasum testfile | tee checksums")
+
+      server.succeed('curl --fail http://localhost:9001 -X POST -F "api=upload" -F "dir=" -F "file=@testfile" | grep "OK"');
+      server.succeed("rm testfile")
+
+      server.succeed('curl --fail http://localhost:9001 -X POST -F "api=download" -F "filename=testfile" -F "dir=" --output testfile');
+      server.succeed("shasum --check checksums")
+    '';
 }