tweak nextcloud and psql settings

nixos/server/nextcloud.nix

···
     datadir = "/mnt/stuff/nextcloud";
     phpOptions = {
       "opcache.interned_strings_buffer" = "16";
+      "pm.max_children" = "48";
+      "pm.start_servers" = "20";
+      "pm.min_spare_servers" = "10";
+      "pm.max_spare_servers" = "36";
     };
     caching = {
       apcu = true;

nixos/server/postgresql.nix

···
         ensureDBOwnership = true;
       }
     ];
+    settings = {
+      max_connections = 5000;
+    };
   };
 }