Adding docs for REPORTING_DIR settings

documentation/operator-guide/configuration.rst

@@ -193,6 +193,8 @@ parts.
   to.
 * ``DJANGO_USER``, ``DJANGO_MAIL``, ``DJANGO_PASSWORD`` -
   The Django admin user account credentials to use the Admin GUI.
+* ``REPORTING_DIR`` -
+  This sets the directory to write the reports of the registered products to.
 
 .. note::
   These variables are used during the initial stack setup. When these