Triggers when a membership status is being changed. This filter allows you to change the value of the new status before it is changed in the database.
Parameters:
- $new_status (string) - New status being set ('active', 'expired', etc.).
- $old_status (string) - Old status from before the change. (Technically the current status, as the status has not yet been edited.)
- $membership_id (int) - ID of the membership being edited.
- $membership (RCP_Membership) - Membership object.