Setup mail server and restructure some things

config/hosts/coturn/configuration.nix

@@ -0,0 +1,22 @@
+{ config, ... }:
+{
+  boot.loader.grub = {
+    enable = true;
+    device = "/dev/vda";
+  };
+
+  networking = {
+    hostName = "coturn";
+    firewall = {
+      enable = true;
+      allowedTCPPorts = [ 80 3478 5349 ];
+      allowedUDPPorts = [ 3478 5349 ];
+      allowedUDPPortRanges = [{
+        from = config.services.coturn.min-port;
+        to = config.services.coturn.max-port;
+      }];
+    };
+  };
+
+  system.stateVersion = "23.05";
+}