[IMP] cli tools: default 'postgres' database.

Rational: when calling oow psql, sometimes, we don't want to put a database. Example, if we call "oow -d postgres -c 'psql'".
In that case, this improvment makes that default postgres database will be proposed in the 'prompt', if no database is provided

newsfragments/+improving-psql-command-default-db.misc

@@ -0,0 +1,2 @@
+set a default 'postgres' database in ``oow psql`` command, to avoid force user
+to set a database, in case of dbless command.

odoo_openupgrade_wizard/cli/cli_options.py

@@ -59,6 +59,7 @@ def database_option_required(function):
         "--database",
         required=True,
         prompt=True,
+        default="postgres",
         type=str,
         help="Odoo Database for which you want to perform the operation.",
     )(function)