(Exploratory) An admin can specify the default forum subscription mode

This is an explanatory test for Moodle 3.4. 

1. As an administrator, access the Forum settings from the Plugins area of Site administration.
2. Change Subscription mode to Forced.
3. Navigate to a course and create a new forum.
4. Expand Subscription and tracking and verify that in Subscription mode the first option in the dropdown is Forced subscription.
5. Verify that you can change the mode to a different option.
6. Repeat steps 1 -5 but with a different default subscription mode, ensuring you create a new forum in step 3.
7. Explore further if possible.