SW-957: by default, expire message after 5 days

LCS/Messaging/python/messaging/messages.py

@@ -59,7 +59,7 @@ class LofarMessage:
         self.content = content
         self.subject = subject
         self.priority = priority
-        self.ttl = ttl
+        self.ttl = ttl if ttl is not None else 5*24*60*60 # by default, expire message after 5 days. 
         self.id = uuid.uuid4() if id is None else uuid.UUID(id)
 
     def as_kombu_publish_kwargs(self):