Add mqtt service to magnesium

hosts/magnesium/services/default.nix

@@ -1,6 +1,7 @@
 {
   imports = [
     ./coturn.nix
+    ./mosquitto.nix
     ./public-ip-tunnel.nix
     ./webserver.nix
   ];

hosts/magnesium/services/mosquitto.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+let port = 1883;
+in
+{
+  services.mosquitto = {
+    enable = true;
+    persistence = true;
+    listeners = [
+      {
+        port = port;
+      }
+    ];
+  };
+  networking.firewall.allowedTCPPorts = [ port ];
+}