✨(backend) add metadata collection of VAD, connection and chat events

Introduce MetadataCollector and MetadataCollectorService classes to
centralize the collection and storage of user connections, VAD events,
and chat messages. This creates a structured foundation for future speaker
assignment logic based on voice activity detection. Add tests for this new
feature.

src/backend/core/recording/services/metadata_collector.py

@@ -0,0 +1,91 @@
+"""Meeting metadata collection service."""
+
+from logging import getLogger
+
+from django.conf import settings
+
+from asgiref.sync import async_to_sync, sync_to_async
+from livekit.protocol.agent_dispatch import (
+    CreateAgentDispatchRequest,
+)
+
+from core import utils
+from core.models import Recording
+
+logger = getLogger(__name__)
+
+
+class MetadataCollectorException(Exception):
+    """Generic exception in the metadata collector."""
+
+
+class MetadataCollectorService:
+    """Service for dispatching and managing the metadata collector agent."""
+
+    @async_to_sync
+    async def start(self, recording: Recording):
+        """Explicitly dispatch the metadata collector agent to a room."""
+
+        lkapi = utils.create_livekit_client()
+        room_id = str(recording.room.id)
+
+        try:
+            response = await lkapi.agent_dispatch.create_dispatch(
+                CreateAgentDispatchRequest(
+                    agent_name=settings.METADATA_COLLECTOR_AGENT_NAME,
+                    room=room_id,
+                    metadata=str(recording.id),
+                )
+            )
+        except Exception as e:
+            logger.exception(
+                "Failed to create metadata collector agent for room %s", room_id
+            )
+            raise MetadataCollectorException(
+                "Failed to create metadata collector agent"
+            ) from e
+        finally:
+            await lkapi.aclose()
+
+        dispatch_id = getattr(response, "id", None)
+
+        if not dispatch_id:
+            logger.error("LiveKit response missing dispatch ID for room %s", room_id)
+            raise MetadataCollectorException(
+                f"LiveKit did not return a dispatch_id for room {room_id}"
+            )
+
+        recording.options["metadata_collector_dispatch_id"] = dispatch_id
+        await sync_to_async(recording.save)(update_fields=["options"])
+
+        return dispatch_id
+
+    @async_to_sync
+    async def stop(self, recording: Recording):
+        """Stop and delete the agent dispatch associated to the room."""
+
+        room_id = str(recording.room.id)
+        dispatch_id = recording.options.get("metadata_collector_dispatch_id")
+        lkapi = utils.create_livekit_client()
+
+        try:
+            if not dispatch_id:
+                logger.warning(
+                    "No metadata collector dispatch ID stored for room %s", room_id
+                )
+                return None
+
+            await lkapi.agent_dispatch.delete_dispatch(
+                dispatch_id=str(dispatch_id), room_name=room_id
+            )
+
+        except Exception as e:
+            logger.exception(
+                "Failed to stop metadata collector agent dispatch for room %s",
+                room_id,
+            )
+            raise MetadataCollectorException(
+                f"Failed to stop metadata collector agent for room {room_id}"
+            ) from e
+        finally:
+            await lkapi.aclose()

src/backend/core/recording/services/recording_events.py

@@ -7,6 +7,7 @@ from logging import getLogger
 from livekit import api
 
 from core import models, utils
+from core.models import Recording
 
 logger = getLogger(__name__)
 
@@ -19,7 +20,7 @@ class RecordingEventsService:
     """Handles recording-related LiveKit webhook events."""
 
     @staticmethod
-    def handle_update(recording, egress_status):
+    def handle_update(recording: Recording, egress_status):
         """Handle egress status updates and sync recording state to room metadata."""
 
         room_name = str(recording.room.id)
@@ -40,7 +41,7 @@ class RecordingEventsService:
                 logger.exception("Failed to update room's metadata: %s", e)
 
     @staticmethod
-    def handle_limit_reached(recording):
+    def handle_limit_reached(recording: Recording):
         """Stop recording and notify participants when limit is reached."""
 
         recording.status = models.RecordingStatusChoices.STOPPED