clanModules/importer: Init importer inventory module

Initialize the `importer` inventory module.
It is a power user module that allows for convenient, flexible,
structured imports for hosts.

It exposes the `extraModules` functionality of the inventory,
without any added configuration.

Closes: #2356

clanModules/flake-module.nix

@@ -13,6 +13,7 @@
     golem-provider = ./golem-provider;
     heisenbridge = ./heisenbridge;
     iwd = ./iwd;
+    importer = ./importer;
     localbackup = ./localbackup;
     localsend = ./localsend;
     matrix-synapse = ./matrix-synapse;

clanModules/importer/README.md

@@ -0,0 +1,27 @@
+---
+description = "Convenient, structured module imports for hosts."
+categories = ["Utility"]
+features = [ "inventory" ]
+---
+The importer module allows users to configure importing modules in a flexible and structured way.
+
+It exposes the `extraModules` functionality of the inventory, without any added configuration.
+
+## Usage:
+
+```nix
+inventory.services = {
+  importer.base = {
+    roles.default.tags = [ "all" ];
+    roles.default.extraModules = [ "modules/base.nix" ];
+  };
+  importer.zone1 = {
+    roles.default.tags = [ "zone1" ];
+    roles.default.extraModules = [ "modules/zone1.nix" ];
+  };
+};
+```
+
+This will import the module `modules/base.nix` to all machines that have the `all` tag,
+which by default is every machine managed by the clan.
+And also import for all machines tagged with `zone1` the module at `modules/zone1.nix`.

clanModules/importer/default.nix

@@ -0,0 +1,4 @@
+# Dont import this file
+# It is only here for backwards compatibility.
+# Dont author new modules with this file.
+{ }

clanModules/importer/roles/default.nix

@@ -0,0 +1 @@
+{ }

docs/mkdocs.yml

@@ -79,6 +79,7 @@ nav:
           - reference/clanModules/heisenbridge.md
           - reference/clanModules/index.md
           - reference/clanModules/iwd.md
+          - reference/clanModules/importer.md
           - reference/clanModules/localbackup.md
           - reference/clanModules/localsend.md
           - reference/clanModules/machine-id.md