fix: Improve handling of Redis URL

This change replaces the creation of Redis URL, from a simple string
interpolation, to using `yarl.URL`. The main benefit, besides not
forgetting to set all five different variables on every Redis client
initialization, is that user credentials are correctly URL-encoded, if
present.

Up until now, if a password had special characters, it could break the
generated URL.

This change also introduces support for a `REDIS_SSL` setting, which
allows the user to specify if the Redis connection should use SSL or not.

backend/handler/socket_handler.py

@@ -1,5 +1,5 @@
 import socketio  # type: ignore
-from handler.redis_handler import redis_url
+from config import REDIS_URL
 
 
 class SocketHandler:
@@ -9,7 +9,7 @@ class SocketHandler:
             async_mode="asgi",
             logger=False,
             engineio_logger=False,
-            client_manager=socketio.AsyncRedisManager(redis_url),
+            client_manager=socketio.AsyncRedisManager(str(REDIS_URL)),
         )
 
         self.socket_app = socketio.ASGIApp(