flake.nix: Centralize overlays

lib/flake-helper.nix

@@ -1,4 +1,4 @@
-{ self, nixpkgs, bij, chaosevents, fernglas, fieldpoc, nixos-exporter, solid-xmpp-alarm, sops-nix, ... }@inputs:
+{ self, nixpkgs, fernglas, fieldpoc, nixos-exporter, solid-xmpp-alarm, sops-nix, ... }@inputs:
 
 rec {
   generateNixosSystem = {
@@ -26,13 +26,8 @@ rec {
       ../users/clerie
       ({ ... }: {
         nixpkgs.overlays = [
+          self.overlays.nixfilesInputs
           self.overlays.clerie
-          (_: _: {
-            inherit (bij.packages."${system}")
-              bij;
-            inherit (chaosevents.packages."x86_64-linux")
-              chaosevents;
-           })
         ];
         clerie.monitoring = nixpkgs.lib.attrsets.optionalAttrs (group != null) { serviceLevel = group; };
       })