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/openai_realtime/websocket.py

@@ -0,0 +1,51 @@
+"""UTF-8 JSON serializer and transport builder for public Realtime WebSockets."""
+
+from __future__ import annotations
+
+import json
+from typing import Any
+
+from fastapi import WebSocket
+from pipecat.frames.frames import (
+    Frame,
+    InputTransportMessageFrame,
+    OutputTransportMessageFrame,
+    OutputTransportMessageUrgentFrame,
+)
+from pipecat.serializers.base_serializer import FrameSerializer
+
+from services.pipecat.transports import build_serialized_ws_transport
+
+
+class OpenAIRealtimeJSONSerializer(FrameSerializer):
+    async def serialize(self, frame: Frame) -> str | bytes | None:
+        if self.should_ignore_frame(frame):
+            return None
+        if isinstance(
+            frame,
+            (OutputTransportMessageFrame, OutputTransportMessageUrgentFrame),
+        ) and isinstance(frame.message, dict):
+            return json.dumps(frame.message, ensure_ascii=False, separators=(",", ":"))
+        return None
+
+    async def deserialize(self, data: str | bytes) -> Frame | None:
+        if isinstance(data, bytes):
+            message: Any = {
+                "type": "_invalid_binary_frame",
+                "event_id": None,
+            }
+        else:
+            try:
+                message = json.loads(data)
+            except json.JSONDecodeError:
+                message = {"type": "_invalid_json", "event_id": None}
+        return InputTransportMessageFrame(message=message)
+
+
+def build_openai_websocket_transport(websocket: WebSocket):
+    return build_serialized_ws_transport(
+        websocket,
+        serializer=OpenAIRealtimeJSONSerializer(),
+        sample_rate=24000,
+    )
+