IQSS#6083 update examples for 'List Role Assignments in a Dataverse' …

…section of Native API.

doc/sphinx-guides/source/api/native-api.rst

@@ -252,8 +252,18 @@ List all the role assignments at the given dataverse::
 
 .. code-block:: bash
 
+  export API_TOKEN=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+  export SERVER_URL=https://demo.dataverse.org
+  export id=root
+
   curl -H X-Dataverse-key:$API_TOKEN $SERVER/api/dataverses/$id/assignments
-  
+
+The fully expanded example above (without environment variables) looks like this:
+
+.. code-block:: bash
+
+  curl -H X-Dataverse-key:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx https://demo.dataverse.org/api/dataverses/root/assignments
+
 Assign Default Role to User Creating a Dataset in a Dataverse
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~