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/webrtc.py

@@ -0,0 +1,26 @@
+"""Project-local SmallWebRTC specialization for the OpenAI event channel."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from pipecat.transports.smallwebrtc.connection import SmallWebRTCConnection
+
+
+class OpenAIRealtimeWebRTCConnection(SmallWebRTCConnection):
+    """Prevent Pipecat's private signalling envelope from leaking to clients."""
+
+    data_channel_label = "oai-events"
+
+    def _setup_listeners(self):
+        super()._setup_listeners()
+
+        @self._pc.on("datachannel")
+        def require_openai_event_channel(channel):
+            if channel.label != self.data_channel_label:
+                channel.close()
+
+    def send_app_message(self, message: Any):
+        if isinstance(message, dict) and message.get("type") == "signalling":
+            return
+        super().send_app_message(message)