porfolio/export: Add info about export queue

New feature in Mahara 1.10 (Bug #1335670) to
export Leap2A exports via a queue.

source/administration/config_site.rst

@@ -83,6 +83,7 @@ Site settings
 .. _masquerading_reason_setting:
 .. _masquerading_notification_setting:
 .. _profile_completion_siteadmin:
+.. _export_to_queue:
 
 User settings
 ^^^^^^^^^^^^^^^^^^

source/portfolio/export.rst

@@ -49,3 +49,5 @@ Depending on the size of your portfolio, the export may take a little bit. Once
 
 .. note::
    If your export gets stuck in the process and the progress bar does not move along at all, your server settings may prevent long operations to avoid slowing down the entire system. You will need to contact your site administrator, e.g. via the "Contact us" form in the footer of the page.
+
+|new in Mahara 1.10| **Experimental feature**: :index:`If <single: New in Mahara 1.10; Export Leap2A via queue>` your site administrator enabled the feature to :ref:`queue Leap2A exports <export_to_queue>`, you will receive a notification when the export has finished. You then have 24 hours until the link to the archive expires. If you do not download your export within that time frame, you will need to export your content again.