Refa: restore openai-compatible chat completions api (#14380)

### What problem does this PR solve?
restore openai-compatible chat completions api
### Type of change

- [x] Refactoring

docs/references/http_api_reference.md

@@ -33,7 +33,7 @@ A complete reference for RAGFlow's RESTful API. Before proceeding, please ensure
 
 ### Create chat completion
 
-**POST** `/api/v1/chats_openai/{chat_id}/chat/completions`
+**POST** `/api/v1/openai/{chat_id}/chat/completions`
 
 Creates a model response for a given chat conversation.
 
@@ -42,7 +42,7 @@ This API follows the same request and response format as OpenAI's API. It allows
 #### Request
 
 - Method: POST
-- URL: `/api/v1/chats_openai/{chat_id}/chat/completions`
+- URL: `/api/v1/openai/{chat_id}/chat/completions`
 - Headers:
   - `'content-Type: application/json'`
   - `'Authorization: Bearer <YOUR_API_KEY>'`
@@ -56,11 +56,11 @@ This API follows the same request and response format as OpenAI's API. It allows
 
 ```bash
 curl --request POST \
-     --url http://{address}/api/v1/chats_openai/{chat_id}/chat/completions \
+     --url http://{address}/api/v1/openai/{chat_id}/chat/completions \
      --header 'Content-Type: application/json' \
      --header 'Authorization: Bearer <YOUR_API_KEY>' \
      --data '{
-        "model": "model",
+        "model": "glm-4-flash@ZHIPU-AI",
         "messages": [{"role": "user", "content": "Say this is a test!"}],
         "stream": true,
         "extra_body": {
@@ -85,8 +85,11 @@ curl --request POST \
 
 ##### Request Parameters
 
+- `chat_id` (*Path parameter*) `string`, *Required*
+  Existing chat assistant ID. The request will use that chat assistant's knowledge and settings.
+
 - `model` (*Body parameter*) `string`, *Required*
-  The model used to generate the response. The server will parse this automatically, so you can set it to any value for now.
+  The model used to generate the response. When `chat_id` is provided, you may also use the legacy placeholder value `"model"` to keep using the chat assistant's configured model.
 
 - `messages` (*Body parameter*) `list[object]`, *Required*
   A list of historical chat messages used to generate the response. This must contain at least one message with the `user` role.

docs/references/python_api_reference.md

@@ -46,9 +46,13 @@ Creates a model response for the given historical chat conversation via OpenAI's
 
 #### Parameters
 
+##### chat_id: `string`, *Required*
+
+Existing chat assistant ID. This value is part of the request path: `/api/v1/openai/<chat_id>/chat/completions`.
+
 ##### model: `string`, *Required*
 
-The model used to generate the response. The server will parse this automatically, so you can set it to any value for now.
+The model used to generate the response. You may also use the legacy placeholder value `"model"` to keep using the chat assistant's configured model.
 
 ##### messages: `list[object]`, *Required*
 
@@ -65,20 +69,12 @@ Whether to receive the response as a stream. Set this to `false` explicitly if y
 
 #### Examples
 
-> **Note**
-> Streaming via `client.chat.completions.create(stream=True, ...)` does not
-> return `reference` currently because `reference` is only exposed in the
-> non-stream response payload. The only way to return `reference` is non-stream
-> mode with `with_raw_response`.
-:::caution NOTE
-Streaming via `client.chat.completions.create(stream=True, ...)` does not return `reference` because it is *only* included in the raw response payload in non-stream mode. To return `reference`, set `stream=False`.
-:::
 ```python
 from openai import OpenAI
 import json
 
-model = "model"
-client = OpenAI(api_key="ragflow-api-key", base_url=f"http://ragflow_address/api/v1/chats_openai/<chat_id>")
+model = "glm-4-flash@ZHIPU-AI"
+client = OpenAI(api_key="ragflow-api-key", base_url="http://ragflow_address/api/v1/openai/<chat_id>/chat")
 
 stream = True
 reference = True
@@ -92,13 +88,11 @@ request_kwargs = dict(
         {"role": "user", "content": "Can you tell me how to install neovim"},
     ],
     extra_body={
-        "extra_body": {
-            "reference": reference,
-            "reference_metadata": {
-                "include": True,
-                "fields": ["author", "year", "source"],
-            },
-        }
+        "reference": reference,
+        "reference_metadata": {
+            "include": True,
+            "fields": ["author", "year", "source"],
+        },
     },
 )
 
@@ -119,6 +113,8 @@ else:
     print("reference:", data["choices"][0]["message"].get("reference"))
 ```
 
+When `extra_body.reference` is `true`, the streamed final chunk may include `choices[0].delta.reference`, and the non-stream response may include `choices[0].message.reference`.
+
 When `extra_body.reference_metadata.include` is `true`, each reference chunk may include a `document_metadata` object in both streaming and non-streaming responses.
 
 ## DATASET MANAGEMENT