root: add Channels Message Storage and consumer

passbook/root/messages/consumer.py

@@ -0,0 +1,20 @@
+"""websocket Message consumer"""
+from channels.generic.websocket import JsonWebsocketConsumer
+from django.core.cache import cache
+
+
+class MessageConsumer(JsonWebsocketConsumer):
+    """Consumer which sends django.contrib.messages Messages over WS.
+    channel_name is saved into cache with user_id, and when a add_message is called"""
+
+    def connect(self):
+        self.accept()
+        cache.set(f"user_{self.scope['user'].pk}_{self.channel_name}", True)
+
+    # pylint: disable=unused-argument
+    def disconnect(self, close_code):
+        cache.delete(f"user_{self.scope['user'].pk}_{self.channel_name}")
+
+    def event_update(self, event: dict):
+        """Event handler which is called by Messages Storage backend"""
+        self.send_json(event)