[IMP] install/maintain: add info about upgrading Odoo Online databases

closes odoo/documentation#1576

Signed-off-by: Castillo Jonathan (jcs) <jcs@odoo.com>

content/administration/maintain/online.rst

@@ -35,14 +35,26 @@ Several actions are available:
 Upgrade
 =======
 
-Upgrade the database to the latest Odoo version.
+If you are *not* on the latest **Online version**, you should receive an invitation to :doc:`upgrade
+<../upgrade/process>` your database. A **Rolling Release button** on your database's main screen
+proposes an upgrade to the latest version (e.g., 13.0 to 15.1).
 
-.. warning::
+.. important::
-   Upgrading a database to a newer version of Odoo is a complex operation that requires time and
+   - | **If your Odoo database's version is lower than the latest major release:**
-   caution. It is essential to test the upgrade before upgrading the production database.
+     | You must upgrade your database within two months. After these two months, an automatic
+       upgrade is initiated.
+   - | **If your Odoo database's version is equal to or higher than the latest major release:**
+     | You can disregard the invitation to upgrade as you probably wouldn't benefit from new
+       features every two months.
+
+.. note::
+   Versions that are not supported anymore become deprecated and need to be updated to avoid
+   security issues. We recommend you initiate the upgrade of the database yourself, as this method
+   allows you to request a test upgrade of your database to check for any discrepancies.
 
 .. seealso::
    - :doc:`../upgrade/process`
+   - :doc:`supported_versions`
 
 .. _online/duplicate:
 

content/administration/maintain/supported_versions.rst

@@ -8,10 +8,13 @@ Supported versions
 Odoo provides support and bug fixing **for the 3 last major versions** of Odoo.
 
 .. note::
-   Odoo also releases intermediary versions (called *SaaS versions*) on the Odoo Online hosting
+   Odoo releases intermediary versions called **Online versions** on the :doc:`Odoo Online <online>`
-   every two months. Users on Odoo Online can then benefit from latest features of Odoo. Only the
+   hosting every two months. Odoo Online users can then benefit from the latest features of Odoo.
-   latest SaaS version is supported. Users hosted on Odoo Online are then invited to upgrade
+
-   regularly. These versions are not published for Odoo.sh and On-Premise installations.
+   - Admins of Odoo Online databases are invited to :doc:`upgrade <../upgrade/process>` them
+     regularly.
+   - Online versions are *not* released for Odoo.sh and On-Premise installations.
+   - Online versions are listed below as *SaaS*.
 
 What's the support status of my Odoo?
 =====================================