feat: introduce shared global variable aggregator with recursive redistribution

flake.nix

@@ -141,6 +141,25 @@
       # Add a shorthand to easily target toplevel derivations
       "@" = mapAttrs (_: v: v.config.system.build.toplevel) self.nodes;
 
+      globals = let
+        globalsSystem = nixpkgs.lib.evalModules {
+          prefix = ["globals"];
+          modules = [
+            ./modules/globals.nix
+            ({lib, ...}: {
+              globals = lib.mkMerge (
+                lib.concatLists (lib.flip lib.mapAttrsToList self.nodes (
+                  name: cfg:
+                    builtins.addErrorContext "while aggregating globals from nixosConfigurations.${name} into flake-level globals:"
+                    cfg.config._globalsDefs
+                ))
+              );
+            })
+          ];
+        };
+      in
+        globalsSystem.config.globals;
+
       # For each true NixOS system, we want to expose an installer package that
       # can be used to do the initial setup on the node from a live environment.
       # We use the minimal sibling configuration to reduce the amount of stuff

modules/default.nix

@@ -9,6 +9,7 @@
     ./backups.nix
     ./deterministic-ids.nix
     ./distributed-config.nix
+    ./globals.nix
     ./kanidm.nix
     ./meta.nix
     ./netbird-client.nix

modules/globals.nix

@@ -0,0 +1,46 @@
+{
+  lib,
+  options,
+  ...
+}: let
+  inherit
+    (lib)
+    mkOption
+    types
+    ;
+in {
+  options = {
+    globals = mkOption {
+      default = {};
+      type = types.submodule {
+        options = {
+          services = mkOption {
+            type = types.attrsOf (types.submodule {
+              options = {
+                domain = mkOption {
+                  type = types.str;
+                  description = "";
+                };
+              };
+            });
+
+            #telegrafChecks = mkOption {
+            #  type = types.attrsOf (types.submodule {
+            #    options = {
+            #      domain = mkOption {};
+            #    };
+            #  });
+            #};
+          };
+        };
+      };
+    };
+
+    _globalsDefs = mkOption {
+      type = types.unspecified;
+      default = options.globals.definitions;
+      readOnly = true;
+      internal = true;
+    };
+  };
+}

nix/hosts.nix

@@ -19,7 +19,7 @@ inputs: let
       specialArgs = {
         # Use the correct instance lib that has our overlays
         inherit (pkgs) lib;
-        inherit (self) nodes;
+        inherit (self) nodes globals;
         inherit inputs minimal;
       };
       modules = [