add modules

common/modules/meta.nix

@@ -0,0 +1,43 @@
+{ lib, ... }:
+with lib;
+let
+  exposesOpts = {
+    options = {
+      domain = mkOption {
+        type = types.str;
+        example = "<name>.example.com";
+        description = ''
+          The domain under which this service should be available
+        '';
+      };
+      port = mkOption {
+        type = types.int;
+        default = 80;
+        example = 4242;
+        description = ''
+          The port under which the service runs on the host
+        '';
+      };
+    };
+  };
+in
+{
+  options.meta = {
+
+    exposes = mkOption {
+      type = with types; attrsOf (submodule exposesOpts);
+      description = ''
+        Exposed services
+      '';
+    };
+
+    ipv4 = mkOption {
+      type = types.str;
+      description = ''
+        Own IPv4 Address
+      '';
+    };
+  };
+
+  config = { };
+}