change default for DASF_STORE_MESSAGES to cache

dasf_broker/app_settings.py

@@ -59,4 +59,4 @@ DASF_CREATE_TOPIC_ON_MESSAGE = getattr(
 #: ``"store"``
 #:     The message and response topics are stored forever and are not
 #:     automatically removed
-DASF_STORE_MESSAGES = "store"
+DASF_STORE_MESSAGES = getattr(settings, "DASF_STORE_MESSAGES", "cache")