fix multipart/form-data decoding

packages/backend/src/misc/create-temp.ts

@@ -3,6 +3,8 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
+import { pipeline } from 'node:stream/promises';
+import fs from 'node:fs';
 import * as tmp from 'tmp';
 
 export function createTemp(): Promise<[string, () => void]> {
@@ -27,3 +29,14 @@ export function createTempDir(): Promise<[string, () => void]> {
 		);
 	});
 }
+
+export async function saveToTempFile(stream: NodeJS.ReadableStream): Promise<string> {
+	const [filepath, cleanup] = await createTemp();
+	try {
+		await pipeline(stream, fs.createWriteStream(filepath));
+		return filepath;
+	} catch (e) {
+		cleanup();
+		throw e;
+	}
+}