hydra: upgrade postgres

hosts/hydra/default.nix

@@ -1,4 +1,4 @@
-{ config, lib, ... }:
+{ config, lib, pkgs, ... }:
 
 let
   cachePort = 5000;
@@ -237,6 +237,11 @@ in
 
     portunus.addToHosts = true;
 
+    postgresql = {
+      package = pkgs.postgresql_15;
+      upgrade.stopServices = [ "hydra-evaluator" "hydra-queue-runner" "hydra-server" ];
+    };
+
     resolved.enable = false;
 
     smartd.enable = true;