Minor improvements (#381)

* Minor improvements

* Document empty list vs null for users without privileges

* Change the wording for null values

* Add talk by Oleksii in Atmosphere

docs/developer.md

@@ -275,3 +275,12 @@ Type 'help' for list of commands.
 (dlv) c
 PASS
 ```
+
+To test the multinamespace setup, you can use
+```
+./run_operator_locally.sh --rebuild-operator
+```
+It will automatically create an `acid-minimal-cluster` in the namespace `test`. Then you can for example check the Patroni logs:
+```
+kubectl logs acid-minimal-cluster-0 
+```