[IMP] core: config option for system database

odoo/odoo#239487

content/developer/reference/cli.rst

@@ -318,6 +318,11 @@ Database
     when creating new databases from the database-management screens, use the
     specified `template database`_. Defaults to ``template0``.
 
+.. option:: --db-system <db>
+
+    specify the database for shared system operations like bus and maintenance.
+    Defaults to ``postgres``.
+
 .. option:: --pg_path </path/to/postgresql/binaries>
 
     Path to the PostgreSQL binaries that are used by the database manager to