chore: move postgresql config to own file

configuration.nix

@@ -9,6 +9,7 @@ in
     (import ./acme.nix { inherit base-domain; })
     (import ./nginx.nix { inherit base-domain; })
     (import ./sourcehut.nix { inherit base-domain; })
+    ./postgresql.nix
     ./userprogs.nix
   ];
 

postgresql.nix

@@ -0,0 +1,3 @@
+{
+  services.postgresql.enable = true;
+}

sourcehut.nix

@@ -42,6 +42,4 @@ in
       webhooks.private-key = "/etc/nixos/secrets/sourcehut/webhook.key";
     };
   };
-
-  services.postgresql.enable = true;
 }