support sequence2txt and tts model in Xinference (#2696)

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

rag/llm/tts_model.py

@@ -297,3 +297,36 @@ class SparkTTS:
                     break
             status_code = 1
             yield audio_chunk
+
+
+
+
+class XinferenceTTS:
+    def __init__(self, key, model_name, **kwargs):
+        self.base_url = kwargs.get("base_url", None)
+        self.model_name = model_name
+        self.headers = {
+            "accept": "application/json",
+            "Content-Type": "application/json"
+        }
+
+    def tts(self, text, voice="中文女", stream=True):
+        payload = {
+            "model": self.model_name,
+            "input": text,
+            "voice": voice
+        }
+
+        response = requests.post(
+            f"{self.base_url}/v1/audio/speech",
+            headers=self.headers,
+            json=payload,
+            stream=stream
+        )
+
+        if response.status_code != 200:
+            raise Exception(f"**Error**: {response.status_code}, {response.text}")
+
+        for chunk in response.iter_content(chunk_size=1024):
+            if chunk:
+                yield chunk