feat: implement OpenAI-compatible Realtime API with authentication and management features

- Added support for public Realtime API, including new routes for managing API keys and handling WebRTC connections.
- Introduced RealtimeApiKey model and associated CRUD operations for admin management of API keys.
- Implemented authentication mechanisms for API keys and client secrets.
- Enhanced environment configuration with new secrets for Realtime API.
- Created OpenAIRealtime session management and event processing for real-time interactions.
- Updated schemas and settings to accommodate new features and ensure compatibility with existing systems.

backend/services/pipecat/transports.py

@@ -25,6 +25,7 @@ from pipecat.transports.websocket.fastapi import (
     FastAPIWebsocketTransport,
     FastAPIWebsocketParams,
 )
+from pipecat.serializers.base_serializer import FrameSerializer
 from pipecat.serializers.protobuf import ProtobufFrameSerializer
 
 from services.pipecat.call_lifecycle import FixedSpeechPlaybackMarkerFrame
@@ -103,10 +104,33 @@ def build_ws_transport(websocket: WebSocket) -> FastAPIWebsocketTransport:
     """裸 WS 输出。序列化用 protobuf(自定义客户端用同款解码);
     若对接电话商,把 serializer 换成对应的 TwilioFrameSerializer 等即可。
     """
+    return build_serialized_ws_transport(
+        websocket,
+        serializer=ProtobufFrameSerializer(),
+    )
+
+
+def build_serialized_ws_transport(
+    websocket: WebSocket,
+    *,
+    serializer: FrameSerializer,
+    sample_rate: int | None = None,
+) -> FastAPIWebsocketTransport:
+    """Build a text/binary WS transport without coupling it to one protocol."""
+
+    sample_rates = (
+        {
+            "audio_in_sample_rate": sample_rate,
+            "audio_out_sample_rate": sample_rate,
+        }
+        if sample_rate
+        else {}
+    )
     return _WebsocketTransport(
         websocket=websocket,
         params=FastAPIWebsocketParams(
-            serializer=ProtobufFrameSerializer(),
+            serializer=serializer,
             **_base_params(),
+            **sample_rates,
         ),
     )