How do I split common system configuration into seperate files

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In my configuration.nix

{ config, lib, pkgs, ... }:

{
  nix = {
    extraOptions = ''
      experimental-features = nix-command flakes
      min-free = ${toString (100 * 1024 * 1024)}
      max-free = ${toString (1024 * 1024 * 1024)}
    '';
  };
  imports =
    [
      # Include the results of the hardware scan.
      ./hardware-configuration.nix
      ../../common
    ];
# ...

My ./common/default.nix

{config, lib, pkgs, ...}:
{

  ##### Programs #####
  virtualisation = {
    podman = {
      enable = true; 
      # dockerCompat = true; # can conflict with docker
      defaultNetwork.settings = {
        dns_enable = true;
      };
    };
  };

  config.services.postgresql = {
    enable = true;
    ensureDatabases = [ "scratchdb" ];
    authentication = pkgs.lib.mkOverride 10 ''
      #type database  DBuser  auth-method
      local all       all     trust
    '';
  };

  ##### End Programs #####
  users.users.redacted = {
    isNormalUser = true;
    description = "redacted";
    extraGroups = [ "redacted" ];
    shell = pkgs.fish;
    packages = with pkgs; [
      firefox
    #  thunderbird
    ];
  };

  programs.fish.enable = true;
  # Allow unfree packages
  nixpkgs.config.allowUnfree = true;

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment.systemPackages = with pkgs; [
  #  vim # Do not forget to add an editor to edit configuration.nix! The Nano editor is also installed by default.
    wget
    git
  ];

  # Enable auto optimiztion for the store
  nix.settings.auto-optimise-store = true;

  # Docker install with rootless
  virtualisation.docker.enable = true;
  virtualisation.docker.rootless = {
    enable = true;
    setSocketVariable = true;
  };

  # Garbage collection can be automated 
  nix.gc = {
    automatic = true;
    dates = "weekly";
    options = "--delete-older-than 30d";
  };

  environment.interactiveShellInit = ''
      	alias v='nvim'
      	alias vi='nvim'
    	alias vim='nvim'
    	alias ls='eza'
    	alias tree='eza -T'
    	alias gst='git status'
	alias lg='lazygit'
  '';
}

The error

error: Module `/nix/store/k31ay31mxnfj0nwy7dmwg61zs1qd7i8v-source/common' has an unsupported attribute `environment'. This is caused by introducing a top-level `config' or `options' attribute. Add configuration attributes immediately on the top level instead, or move all of them (namely: environment nix nixpkgs programs users virtualisation) into the explicit `config' attribute.

This error will pop up for any of the attributes I have set in common. I’m sure I’m just misunderstanding something.