Move overlays to flake definition

flake.nix

@@ -17,7 +17,7 @@
     };
     openconnect-sso = {
       url = "github:vlaci/openconnect-sso";
-      flake = false;
+      inputs.nixpkgs.follows = "nixpkgs";
     };
     cyrus-sasl-xoauth2 = {
       url = "github:robn/sasl2-oauth";
@@ -37,7 +37,18 @@
     let
       system = "x86_64-linux";
 
-      pkgs = import pkgs { inherit system; };
+      pkgs = import nixpkgs {
+        inherit system;
+        config.allowUnfree = true;
+        overlays = [
+          inputs.openconnect-sso.overlay
+          (final: prev: {
+            emacs-vterm =
+              ((pkgs.emacsPackagesFor pkgs.emacs29-pgtk).emacsWithPackages
+                (epkgs: with epkgs; [ vterm ]));
+          })
+        ];
+      };
 
       lib = nixpkgs.lib;
 
@@ -49,7 +60,10 @@
           agenix.nixosModules.age
           nix-index-database.nixosModules.nix-index
         ];
-        specialArgs = { inherit inputs; };
+        specialArgs = {
+          inherit inputs;
+          inherit pkgs;
+        };
       };
 
     };