Cachix not used?

I have the following but authentik gets compiled from source. How can I use the binary cache? ``` flake.nix { inputs = { # Nixpkgs nixpkgs.url = "github:nixos/nixpkgs/nixos-25.11"; authentik-nix = { url = "github:nix-community/authentik-nix"; }; }; outputs = { self, nixpkgs, ... } @ inputs: { nixosConfigurations = { server = nixpkgs.lib.nixosSystem { specialArgs = {inherit inputs outputs;}; modules = [ ./hosts/server ]; }; }; }; } ``` ``` server.nix { config, lib, inputs, ... }: { imports = [ inputs.authentik-nix.nixosModules.default ]; nix.settings.substituters = [ "https://nix-community.cachix.org" ]; nix.settings.trusted-public-keys = [ "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=" ]; services.authentik = { enable = true; }; } ```