server: add data: [DONE] to /chat/completions stream response (#9459)

examples/server/tests/features/steps/steps.py

@@ -1020,6 +1020,8 @@ async def oai_chat_completions(user_prompt,
                             event_data = line.split(': ', 1)
                             assert event_data[0] == 'data', f'Bad event code received: ```{event_data}```'
                             chunk_raw = event_data[1]
+                            if chunk_raw == '[DONE]':
+                                break
 
                             chunk = json.loads(chunk_raw)
                             assert len(chunk['choices']) == 1, f"no choices provided, line ```{line}```"