Documentation update.

doc/getting_started/upgrade.rst

@@ -9,6 +9,8 @@ newest versions of Modoboa.
    Before running a migration, we recommend that you make
    a copy of your existing database.
 
+.. _latestversion:
+
 **************
 Latest version
 **************
@@ -45,6 +47,8 @@ one:
 Don't copy the old *settings.py* file, just keep the new one and
 modify it (see :ref:`database` and :ref:`timezone_lang`).
 
+Migrate your database (see :ref:`latestversion`).
+
 Finally, check the :ref:`amavis_frontend`, :ref:`postfix_ar` and
 :ref:`stats` chapters (depending on those you use) because the
 provided cron scripts have been changed, you must update the way you