modules/prometheus: split exporters and alerts to seperate files

modules/nixos/prometheus/ntfy-sh.nix

@@ -0,0 +1,17 @@
+{ config, lib, ... }:
+let
+  cfg = config.custom.prometheus;
+in
+{
+  config = lib.mkIf cfg.enable {
+    services.ntfy-sh.settings.enable-metrics = true;
+    services.prometheus.scrapeConfigs = [
+      (lib.mkIf cfg.exporters.ntfy-sh.enable {
+        job_name = "ntfy-sh";
+        static_configs = [
+          { targets = [ "ntfy.xinyang.life" ]; }
+        ];
+      })
+    ];
+  };
+}