[ADD] administration: neutralized database

closes odoo/documentation#7305

Task: 3572950
Signed-off-by: Xavier Platteau (xpl) <xpl@odoo.com>

content/administration/maintain.rst

@@ -15,4 +15,5 @@ Maintain
     maintain/hosting_changes
     maintain/odoo_online
     maintain/on_premise
+    maintain/neutralized_database
     maintain/supported_versions

content/administration/maintain/neutralized_database.rst

@@ -0,0 +1,35 @@
+====================
+Neutralized database
+====================
+
+A neutralized database is a non-production database on which several parameters are deactivated.
+This enables one to carry out tests without the risk of launching specific automated processes that
+could impact production data (e.g., sending emails to customers). Live access is removed and
+turned into a testing environment.
+
+.. note::
+   **Any testing database created is a neutralized database:**
+
+   - testing backup databases
+   - duplicate databases
+   - for Odoo.sh: staging and development databases
+
+.. important::
+   A database can also be neutralized when upgrading, as it is vital to do some tests before
+   switching to a new version.
+
+Deactivated features
+====================
+
+Here is a non-exhaustive list of the deactivated parameters:
+
+- all planned actions (e.g., automatic invoicing of subscriptions, mass mailing, etc.)
+- outgoing emails
+- bank synchronization
+- payment providers
+- delivery methods
+- :abbr:`IAP (In-App Purchase)` tokens
+
+.. note::
+   **A red banner at the top of the screen is displayed on the neutralized database so that it can
+   be seen immediately.**