feat: use connection pool instead of a single shared connection

This is useful for multitask environments (like the API), to avoid
conflicts

server/app/consumer.py

@@ -1,10 +1,9 @@
 from core.logging import setup_logging
-from dependencies import get_conn, get_uplink_service, get_mqtt_broker
+from dependencies import get_uplink_service, get_mqtt_broker
 
 setup_logging()
 
 if __name__ == "__main__":
-    conn = get_conn()
     broker = get_mqtt_broker()
     uplink = get_uplink_service()