How do I make a searchable and sortable column based on multiple database fields?

[MGeurts]

On my User model I have the fields firstname and lastname.
The model has a getter attribute name to concatenate both :

public function getNameAttribute() {return implode(' ', array_filter([$this->firstname, $this->surname]));}

I can use this in the PowerGrid table like this :

->addColumn('name', function (User $user) {return $user->name;})

and

Column::make('name', 'name')->sortable()->searchable(),

Searching works fine. But sorting throws an arror because of course there's no field name in the database.

How can I modify the sortable() function to sort on more than 1 column?

Tip: I noticed there is a searchableRaw() function in the PowerGrid core.
Can the above problem be solved by adding an sortableRaw() function?

Thanks for any suggestion!