modules/frontmatter: init module interface as source of frontmatter

lib/frontmatter/interface.nix

@@ -0,0 +1,58 @@
+{
+  lib,
+  specialArgs,
+  ...
+}:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+    description = mkOption {
+      type = types.str;
+      description = ''
+
+      '';
+    };
+    categories = mkOption {
+      default = [ "Uncategorized" ];
+      type = types.listOf (
+        types.enum [
+          "AudioVideo"
+          "Audio"
+          "Video"
+          "Development"
+          "Education"
+          "Game"
+          "Graphics"
+          "Social"
+          "Network"
+          "Office"
+          "Science"
+          "System"
+          "Settings"
+          "Utility"
+          "Uncategorized"
+        ]
+      );
+    };
+    features = mkOption {
+      default = [ ];
+      type = types.listOf (
+        types.enum [
+          "inventory"
+        ]
+      );
+    };
+
+    constraints = mkOption {
+      default = { };
+      type = types.submoduleWith {
+        inherit specialArgs;
+        modules = [
+          ../constraints
+        ];
+      };
+    };
+  };
+}