I am developing a SaaS application and I am looking for the best way to design lookup tables, taking in consideration:

• The look-up tables will have predefined data shared among all the tenants
• Each tenant must have the ability to extend the look-up table with his own data e.g adding a car class not defined

I am thinking about adding TenantID column to each lookup and add the predefined data with setting that column to some value which represents the "Super Tenant" that belongs to the system itself