nextcloud: direct pre-signed download link.

Author: Dr Serge

nixos/modules/services/web-apps/nextcloud.nix

@@ -1324,6 +1324,14 @@ in
               Use `services.nextcloud.secrets.mail_smtppassword` instead and set it to a file containing the password.
             '';
           }
+          {
+            assertion =
+              lib.versionAtLeast cfg.package.version "33.0.0"
+              || cfg.config.objectstore.s3.use_presigned_url != null;
+            message = ''
+              Presigned URLs are only available on Nextcloud >= 33.0.0.
+            '';
+          }
         ];
       }