Initial prometheus config

Also did provision config for grafana, could be done directly but went
through skynet.grafana config

applications/prometheus.nix

@@ -0,0 +1,67 @@
+{
+  lib,
+  config,
+  ...
+}:
+with lib; let
+  name = "prometheus";
+  cfg = config.services.skynet."${name}";
+in {
+  imports = [];
+
+  options.services.skynet."${name}" = {
+    server = {
+      enable = mkEnableOption "Prometheus Server";
+      host = {
+        ip = mkOption {
+          type = types.str;
+        };
+
+        name = mkOption {
+          type = types.str;
+        };
+      };
+
+      port = mkOption {
+        type = types.port;
+        default = 9001;
+      };
+    };
+
+    collecter_port = mkOption {
+      type = types.port;
+      default = 9002;
+    };
+
+    #list of servers passed in for monitoring
+    servers = mkOption {
+      type = types.listOf types.str;
+    };
+  };
+
+  config =
+    {
+      services.prometheus.exporters.node = {
+        enable = true;
+        # most collectors are on by default see docs for more options
+        enabledCollectors = ["systemd"];
+        port = cfg.collecter_port;
+      };
+    }
+    // mkIf cfg.server.enable {
+      services.prometheus = {
+        enable = true;
+        port = cfg.server.port;
+        scrapeConfigs = [
+          {
+            job_name = "node_exporter";
+            static_configs = [
+              {
+                targets = map (server: "${server}.skynet.ie:9002") cfg.servers;
+              }
+            ];
+          }
+        ];
+      };
+    };
+}