feat(server/prometheus): add prometheus module and enable it on apollo

modules/nixos/server/monitoring/prometheus/default.nix

@@ -0,0 +1,19 @@
+{ config, lib, ... }:
+let
+  inherit (lib) mkEnableOption mkIf;
+  inherit (lib.pantheon) mkPortOption;
+  cfg = config.server.monitoring.prometheus;
+in
+{
+  options.server.monitoring.prometheus = {
+    enable = mkEnableOption "";
+    port = mkPortOption 9090;
+  };
+
+  config = mkIf cfg.enable {
+    services.prometheus = {
+      enable = true;
+      inherit (cfg) port;
+    };
+  };
+}

systems/x86_64-linux/apollo/default.nix

@@ -20,9 +20,14 @@
   };
 
   server = {
-    monitoring.grafana = {
+    monitoring = {
-      enable = true;
+      prometheus = {
-      url = "grafana.bwfiq.com";
+        enable = true;
+      };
+      grafana = {
+        enable = true;
+        url = "grafana.bwfiq.com";
+      };
     };
     networking.ddns = {
       enable = true;