chore: import upstream snapshot with attribution

apps/webapp/test/utils/streams.ts

@@ -0,0 +1,46 @@
+export async function convertResponseStreamToArray(response: Response): Promise<string[]> {
+  return convertReadableStreamToArray(response.body!.pipeThrough(new TextDecoderStream()));
+}
+
+export async function convertResponseSSEStreamToArray(response: Response): Promise<string[]> {
+  const parseSSEDataTransform = new TransformStream<string>({
+    async transform(chunk, controller) {
+      for (const line of chunk.split("\n")) {
+        if (line.startsWith("data:")) {
+          controller.enqueue(line.slice(6));
+        }
+      }
+    },
+  });
+
+  return convertReadableStreamToArray(
+    response.body!.pipeThrough(new TextDecoderStream()).pipeThrough(parseSSEDataTransform)
+  );
+}
+
+export async function convertReadableStreamToArray<T>(stream: ReadableStream<T>): Promise<T[]> {
+  const reader = stream.getReader();
+  const result: T[] = [];
+
+  while (true) {
+    const { done, value } = await reader.read();
+    if (done) break;
+    result.push(value);
+  }
+
+  return result;
+}
+
+export function convertArrayToReadableStream<T>(values: T[]): ReadableStream<T> {
+  return new ReadableStream({
+    start(controller) {
+      try {
+        for (const value of values) {
+          controller.enqueue(value);
+        }
+      } finally {
+        controller.close();
+      }
+    },
+  });
+}