Document users are responsible to keep external discovery CM up-to-date (#400)

* Document users are responsible to keep external discovery CM up-to-date

* Update modules/concepts/pages/service_discovery.adoc

Co-authored-by: Felix Hennig <fhennig@users.noreply.github.com>

---------

Co-authored-by: Felix Hennig <fhennig@users.noreply.github.com>

Author: sbernauer

modules/concepts/pages/service_discovery.adoc

@@ -109,6 +109,9 @@ spec:
   ...
 ----
 
+IMPORTANT: It's important that you provide *all* the information in the discovery ConfigMap and that it is up-to-date!
+For Stackable managed services the Stackable Operators will take care of this, but for external service discovery it's your responsibility.
+
 [#whats-next]
 == Further reading