traccar: use postgresql via unix socket

services/traccar.nix

@@ -6,10 +6,10 @@
 {
   imports = [
     (lib.serviceMountWithZpool "traccar" service_configs.zpool_ssds [
-      "/var/lib/private/traccar"
+      "/var/lib/traccar"
     ])
     (lib.serviceFilePerms "traccar" [
-      "Z /var/lib/private/traccar 0700 root root"
+      "Z /var/lib/traccar 0700 traccar traccar"
     ])
     (lib.mkCaddyReverseProxy {
       subdomain = "traccar";
@@ -17,11 +17,38 @@
     })
   ];
 
+  users.users.traccar = {
+    isSystemUser = true;
+    group = "traccar";
+    home = "/var/lib/traccar";
+    description = "Traccar GPS Tracking";
+  };
+  users.groups.traccar = { };
+
+  # PostgreSQL database (auto-created, peer auth via Unix socket)
+  services.postgresql = {
+    ensureDatabases = [ "traccar" ];
+    ensureUsers = [
+      {
+        name = "traccar";
+        ensureDBOwnership = true;
+      }
+    ];
+  };
+
   services.traccar = {
     enable = true;
     settings = {
       web.port = toString service_configs.ports.private.traccar_web.port;
 
+      # PostgreSQL via Unix socket (peer auth, junixsocket is bundled)
+      database = {
+        driver = "org.postgresql.Driver";
+        url = "jdbc:postgresql:///traccar?socketFactory=org.newsclub.net.unix.AFUNIXSocketFactory$FactoryArg&socketFactoryArg=${service_configs.postgres.socket}/.s.PGSQL.5432";
+        user = "traccar";
+        password = "";
+      };
+
       # Only enable OsmAnd protocol (phone app). Prevents Traccar from
       # opening 200+ default protocol ports that conflict with other services.
       protocols.enable = "osmand";
@@ -29,6 +56,17 @@
     };
   };
 
+  # Disable DynamicUser so we can use peer auth with PostgreSQL
+  systemd.services.traccar = {
+    after = [ "postgresql.service" ];
+    requires = [ "postgresql.service" ];
+    serviceConfig = {
+      DynamicUser = lib.mkForce false;
+      User = "traccar";
+      Group = "traccar";
+    };
+  };
+
   # OsmAnd tracking port must be reachable from the internet for the phone app
   networking.firewall.allowedTCPPorts = [
     service_configs.ports.public.traccar_tracking.port