backups: add clanCore backup & clan borgbackup module

nixosModules/clanCore/backups.nix

@@ -0,0 +1,55 @@
+{ lib, ... }:
+{
+  options.clanCore.state = lib.mkOption {
+    default = { };
+    type = lib.types.attrsOf
+      (lib.types.submodule ({ name, ... }: {
+        options = {
+          folder = lib.mkOption {
+            type = lib.types.str;
+            default = name;
+            description = ''
+              Folder where state resides in
+            '';
+          };
+        };
+      }));
+  };
+  options.clanCore.backups = {
+    providers = lib.mkOption {
+      type = lib.types.attrsOf (lib.types.submodule ({ name, ... }: {
+        options = {
+          name = lib.mkOption {
+            type = lib.types.str;
+            default = name;
+            description = ''
+              Name of the backup provider
+            '';
+          };
+          list = lib.mkOption {
+            type = lib.types.str;
+            description = ''
+              script to list backups
+            '';
+          };
+          delete = lib.mkOption {
+            type = lib.types.str;
+            description = ''
+              script to delete a backup
+            '';
+          };
+          start = lib.mkOption {
+            type = lib.types.str;
+            description = ''
+              script to start a backup
+            '';
+          };
+        };
+      }));
+      default = [ ];
+      description = ''
+        Configured backup providers which are used by this machine
+      '';
+    };
+  };
+}