templates: allow specifying from flake-parts module

lib/build-clan/interface.nix

@@ -69,6 +69,15 @@ in
             ```
       '';
     };
+
+    templates = lib.mkOption {
+      type = types.submodule { imports = [ ./templates/interface.nix ]; };
+      default = { };
+      description = ''
+        Define Clan templates.
+      '';
+    };
+
     inventory = lib.mkOption {
       type = types.submodule { imports = [ ../inventory/build-inventory/interface.nix ]; };
       description = ''
@@ -112,11 +121,11 @@ in
       type = types.lazyAttrsOf types.raw;
       default = { };
     };
+
     # flake.clanInternals
     clanInternals = lib.mkOption {
       # Hide from documentation. Exposes internals to the cli.
       visible = false;
-      # type = types.raw;
       # ClanInternals
       type = types.submodule {
         options = {

lib/build-clan/templates/interface.nix

@@ -0,0 +1,57 @@
+{
+  lib,
+  ...
+}:
+let
+  inherit (lib) types;
+
+  templateType = types.submodule (
+    { name, ... }:
+    {
+      options.description = lib.mkOption {
+        type = types.str;
+        default = name;
+        description = ''
+          The name of the template.
+        '';
+      };
+
+      options.path = lib.mkOption {
+        type = types.path;
+        description = ''
+          Holds the path to the clan template.
+        '';
+      };
+    }
+  );
+in
+{
+  options = {
+    # clan.templates.clan
+    clan = lib.mkOption {
+      type = types.attrsOf templateType;
+      default = { };
+      description = ''
+        Holds the different clan templates.
+      '';
+    };
+
+    # clan.templates.disko
+    disko = lib.mkOption {
+      type = types.attrsOf templateType;
+      default = { };
+      description = ''
+        Holds different disko templates.
+      '';
+    };
+
+    # clan.templates.machine
+    machine = lib.mkOption {
+      type = types.attrsOf templateType;
+      default = { };
+      description = ''
+        Holds the different machine templates.
+      '';
+    };
+  };
+}