refactor: expose online backup deletion outcome

lib/online-backup.js

@@ -235,9 +235,9 @@ async function deleteOnlineBackup(key, baseUrl = ONLINE_BACKUP_API_URL, options)
     headers: { 'content-type': 'application/json', accept: 'application/json' },
     body: JSON.stringify({ id: parsed.id, deleteSecret })
   }, options);
-  if (response.status !== 204) {
-    throw new Error(response.status === 404 ? 'Online-Sicherung wurde nicht gefunden' : 'Online-Sicherung konnte nicht gelöscht werden');
-  }
+  if (response.status === 204) return { deleted: true, notFound: false };
+  if (response.status === 404) return { deleted: false, notFound: true };
+  throw new Error('Online-Sicherung konnte nicht gelöscht werden');
 }
 
 module.exports = {

tests/online-backup.test.js

@@ -110,7 +110,7 @@ describe('online backup transport', () => {
 
     await uploadOnlineBackup(created.record, baseUrl);
     const restored = await downloadOnlineBackup(created.key, baseUrl);
-    await deleteOnlineBackup(created.key, baseUrl);
+    assert.deepEqual(await deleteOnlineBackup(created.key, baseUrl), { deleted: true, notFound: false });
 
     assert.deepEqual(restored.settings, settings());
     assert.equal(JSON.stringify(stored).includes(parseOnlineBackupKey(created.key).masterKey.toString('base64url')), false);
@@ -119,6 +119,40 @@ describe('online backup transport', () => {
     assert.equal(requestedUrls.join(' ').includes(stored.id), false);
   });
 
+  it('returns an idempotent outcome when the backup is already missing', async () => {
+    const { createOnlineBackup, deleteOnlineBackup } = require('../lib/online-backup');
+    const server = http.createServer((_request, response) => {
+      response.writeHead(404, { 'content-type': 'application/json' });
+      response.end('{"error":"not_found"}');
+    });
+    servers.push(server);
+    server.listen(0, '127.0.0.1');
+    await once(server, 'listening');
+    const missingBaseUrl = `http://127.0.0.1:${server.address().port}`;
+    const { key } = createOnlineBackup(settings(), '2.0.3');
+
+    assert.deepEqual(await deleteOnlineBackup(key, missingBaseUrl), { deleted: false, notFound: true });
+  });
+
+  it('uses the generic deletion error without reflecting the server response body', async () => {
+    const { createOnlineBackup, deleteOnlineBackup } = require('../lib/online-backup');
+    const server = http.createServer((_request, response) => {
+      response.writeHead(500, { 'content-type': 'application/json' });
+      response.end('{"leaked":"server-secret-value"}');
+    });
+    servers.push(server);
+    server.listen(0, '127.0.0.1');
+    await once(server, 'listening');
+    const baseUrl = `http://127.0.0.1:${server.address().port}`;
+    const { key } = createOnlineBackup(settings(), '2.0.3');
+
+    await assert.rejects(
+      deleteOnlineBackup(key, baseUrl),
+      (error) => error.message === 'Online-Sicherung konnte nicht gelöscht werden'
+        && !error.message.includes('server-secret-value')
+    );
+  });
+
   it('does not reflect server response bodies into client errors', async () => {
     const { createOnlineBackup, uploadOnlineBackup } = require('../lib/online-backup');
     const server = http.createServer((_request, response) => {