chore: PoC to generate d2 network graph

flake.nix

@@ -152,6 +152,18 @@
         nixosConfigurationsMinimal
         ;
 
+      # XXX: WIP: only testing
+      d2diag = let
+        inherit
+          (nixpkgs.lib)
+          attrValues
+          concatLines
+          ;
+      in
+        self.pkgs.x86_64-linux.writeText "test.d2" (
+          concatLines (map (x: x.config.d2diag.text) (attrValues self.nixosConfigurations))
+        );
+
       # All nixosSystem instanciations are collected here, so that we can refer
       # to any system via nodes.<name>
       nodes = self.nixosConfigurations // self.guestConfigs;