Add UPC temperature sensor monitoring

These sensors are part of their air quality measurements, which just
happen to be very close to our server room.

Reviewed-by: Aleix Boné <abonerib@bsc.es>

m/module/upc-qaire-exporter.nix

@@ -0,0 +1,17 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  systemd.services."prometheus-upc-qaire-exporter" = {
+    wantedBy = [ "multi-user.target" ];
+    after = [ "network.target" ];
+    serviceConfig = {
+      Restart = mkDefault "always";
+      PrivateTmp = mkDefault true;
+      WorkingDirectory = mkDefault "/tmp";
+      DynamicUser = mkDefault true;
+      ExecStart = "${pkgs.upc-qaire-exporter}/bin/upc-qaire-exporter";
+    };
+  };
+}