Add mqtt server (mosquitto)

The config was based on the exsisting mosquitto setup.

config/hosts/mqtt/networking.nix

@@ -0,0 +1,20 @@
+{ ... }:
+
+{
+    networking = {
+        interfaces.net0 = {
+            ipv4.addresses = [ {
+                address = "10.31.208.14";
+                prefixLength = 23;
+            } ];
+        };
+        defaultGateway = "10.31.208.1";
+        nameservers = [
+            "10.31.210.1"
+        ];
+    };
+    systemd.network.links."10-net0" = {
+        matchConfig.MACAddress = "BC:24:11:48:85:73";
+        linkConfig.Name = "net0";
+    };
+}