[IMP] Upgrade link technical doc

Author: nmarotte

content/administration/upgrade.rst

@@ -39,8 +39,11 @@ An upgrade does not cover:
   - Migrating from another ERP to Odoo
 
 .. warning::
-   If your database contains a **custom module**, you must first upgrade its source code to be
-   compatible with the new version of Odoo **before upgrading**.
+   If your database contains custom modules, it cannot be upgraded until a version of your custom
+   modules is available for the target version of Odoo. For customers maintaining their own custom
+   modules, we recommend to parallelize the process by :ref:`requesting an upgraded database
+   <upgrade/request-test-database>` while also :ref:`upgrading the source code of your custom
+   modules </developer/howtos/upgrade_modules>`.
 .. TODOUPG : once the page for developers is published, uncomment and link
 .. :doc:`first upgrade its source code </developer/reference/upgrade>`
 
@@ -51,15 +54,15 @@ Upgrading in a nutshell
 #. Request an upgraded test database (see :ref:`obtaining an upgraded test database
    <upgrade/request-test-database>`).
 
+#. (If applicable) : upgrade the source code of your custom module to be compatible with the new
+   version of Odoo (see :ref:`upgrading custom modules <upgrade/upgrade_modules>`).
+
 #. Thoroughly test the upgraded database (see :ref:`testing the new version of the database
    <upgrade/test_your_db>`).
 
 #. Report any issue encountered during the testing to Odoo via the `support page
    <https://odoo.com/help?stage=migration>`__.
 
-#. (If applicable) : upgrade the source code of your custom module to be compatible with the new
-   version of Odoo.
-
 #. Once all issues are resolved and you are confident that the upgraded database can be used as
    your main database without any issues, plan the upgrade of your production database.
 
@@ -69,9 +72,6 @@ Upgrading in a nutshell
 #. Report any issue encountered during the upgrade to Odoo via the `support page
    <https://odoo.com/help?stage=post_upgrade>`__.
 
-.. TODOUPG: Once the page for developers is published, put this at 4)
-.. (see :ref:`upgrading customizations <upgrade/upgrading_customizations>`).
-
 .. _upgrade/request-test-database:
 
 Obtaining an upgraded test database

content/developer/howtos.rst

@@ -20,7 +20,7 @@ How-to guides
     howtos/translations
     howtos/website_themes
     howtos/connect_device
-    howtos/upgrade_module
+    howtos/upgrade_modules
 
 .. cards::
 
@@ -86,7 +86,7 @@ How-to guides
 
       Learn how to enable a module to detect and communicate with an IoT device.
 
-   .. card:: Upgrade a custom module
-      :target: howtos/upgrade_module
+   .. card:: Upgrading custom modules
+      :target: howtos/upgrade_modules
 
       Learn how to upgrade a custom module to a new version of Odoo.