test(nginx): Add simple tests to assert nginx features work

modules/default.nix

@@ -1 +1,6 @@
-{ imports = [ ./crowdsec ]; }
+{
+  imports = [
+    ./crowdsec
+    ./serviceTests/stub.nix
+  ];
+}

modules/serviceTests/mocks.nix

@@ -0,0 +1,27 @@
+/**
+  Module containing mock definitions for service test runners.
+*/
+{ flake-inputs, lib, ... }:
+{
+  imports = [
+    flake-inputs.sops-nix.nixosModules.sops
+    ../.
+    ../../configuration/services/backups.nix
+  ];
+
+  sops.defaultSopsFile = ../../keys/staging.yaml;
+  environment.etc."staging.key" = {
+    mode = "0400";
+    source = ../../keys/hosts/staging.key;
+  };
+  services.openssh = {
+    enable = true;
+    hostKeys = lib.mkForce [
+      {
+        type = "rsa";
+        bits = 4096;
+        path = "/etc/staging.key";
+      }
+    ];
+  };
+}

modules/serviceTests/stub.nix

@@ -0,0 +1,20 @@
+/**
+  Module to make writing service-specific tests easy.
+*/
+{ lib, ... }:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+    serviceTests = mkOption {
+      type = types.attrsOf types.package;
+
+      description = ''
+        NixOS tests to run.
+      '';
+
+      default = { };
+    };
+  };
+}