nixos/syndicate-server: use a static configuration

Configure the server with a configuration path that points into
the Nix store rather than a file that is generated at start-up.

flake.nix

@@ -90,9 +90,25 @@
       with import (nixpkgs + "/nixos/lib/testing-python.nix") {
         inherit system;
         pkgs = pkgs';
-      };
-      {
-        # nothing here
+      }; {
+        simple = simpleTest {
+          name = "http";
+          nodes.machine = { config, pkgs, ... }: {
+            imports = [ self.nixosModules.syndicate-server ];
+
+            nixpkgs.pkgs = pkgs';
+
+            services.syndicate.tty1 = {
+              enable = true;
+              user = "loser";
+              config = [ ];
+            };
+            users.users.loser.isNormalUser = true;
+          };
+          testScript = ''
+            machine.wait_for_job("syndicate-tty1")
+          '';
+        };
       }) { inherit (self.legacyPackages) x86_64-linux; };
   };
 }

nixos/syndicate-server.nix

@@ -49,31 +49,23 @@ with lib;
   config = {
 
     systemd.services = let
-      serverCfgs =
-        lib.attrsets.filterAttrs (_: cfg: cfg.enable) config.services.syndicate;
-    in builtins.listToAttrs (lib.lists.flatten (lib.attrsets.mapAttrsToList
-      (name: cfg:
+      configure = name: cfg:
         let
-          configFileName = "syndicate-nixos-config.pr";
-          runtimeConfig = "\${RUNTIME_DIRECTORY}/${configFileName}";
-          configFile = pkgs.writeText configFileName
+          configFile = lib.pipe cfg.config [
             (lib.strings.concatMapStrings (dir: ''
               <require-service <config-watcher "${dir}" $.>>
-            '') cfg.config);
+            ''))
+            (pkgs.writeText "syndicate-nixos-config.pr")
+          ];
         in [{
           name = "syndicate-${name}";
           value = let
-            serviceConfig = let
-              loadConfig =
-                "${pkgs.coreutils}/bin/cp ${configFile} ${runtimeConfig}";
-            in {
+            serviceConfig = {
               RuntimeDirectory = name;
-              ExecStartPre = loadConfig;
               ExecStart = "${
                   lib.optionalString cfg.runInDbusSession
                   "${pkgs.dbus}/bin/dbus-run-session "
-                }${cfg.package}/bin/syndicate-server --no-banner --config ${runtimeConfig}";
-              ExecReload = loadConfig;
+                }${cfg.package}/bin/syndicate-server --no-banner --config ${configFile}";
               User = cfg.user;
             };
           in {
@@ -106,8 +98,14 @@ with lib;
               WorkingDirectory = "~";
             };
           });
-        }]) (lib.attrsets.filterAttrs (_: cfg: cfg.enable)
-          config.services.syndicate)));
+        }];
+      serverCfgs =
+        lib.attrsets.filterAttrs (_: cfg: cfg.enable) config.services.syndicate;
+    in lib.pipe serverCfgs [
+      (lib.attrsets.mapAttrsToList configure)
+      lib.lists.flatten
+      builtins.listToAttrs
+    ];
 
     systemd.targets.multi-user.wants = lib.lists.flatten
       (lib.attrsets.mapAttrsToList