guarded instead of fillable

app/Nova/City.php

@@ -2,52 +2,53 @@
 
 namespace App\Nova;
 
-use Illuminate\Http\Request;
-use Laravel\Nova\Fields\BelongsTo;
 use Laravel\Nova\Fields\ID;
+use Illuminate\Http\Request;
 use Laravel\Nova\Fields\Text;
+use Laravel\Nova\Fields\BelongsTo;
 
 class City extends Resource
 {
     /**
      * The model the resource corresponds to.
+     *
      * @var string
      */
     public static $model = \App\Models\City::class;
+
     /**
      * The single value that should be used to represent the resource when being displayed.
+     *
      * @var string
      */
     public static $title = 'id';
+
     /**
      * The columns that should be searched.
+     *
      * @var array
      */
     public static $search = [
         'id',
     ];
 
-    public static function label()
-    {
-        return __('Cities');
-    }
-
     /**
      * Get the fields displayed by the resource.
      *
      * @param  \Illuminate\Http\Request  $request
-     *
      * @return array
      */
     public function fields(Request $request)
     {
         return [
-            ID::make()
-              ->sortable(),
+            ID::make()->sortable(),
 
             Text::make('Name')
                 ->rules('required', 'string'),
 
+            Text::make('Slug')
+                ->rules('required', 'string', 'unique:cities,slug'),
+
             BelongsTo::make('Country'),
 
 
@@ -58,7 +59,6 @@ class City extends Resource
      * Get the cards available for the request.
      *
      * @param  \Illuminate\Http\Request  $request
-     *
      * @return array
      */
     public function cards(Request $request)
@@ -70,7 +70,6 @@ class City extends Resource
      * Get the filters available for the resource.
      *
      * @param  \Illuminate\Http\Request  $request
-     *
      * @return array
      */
     public function filters(Request $request)
@@ -82,7 +81,6 @@ class City extends Resource
      * Get the lenses available for the resource.
      *
      * @param  \Illuminate\Http\Request  $request
-     *
      * @return array
      */
     public function lenses(Request $request)
@@ -94,7 +92,6 @@ class City extends Resource
      * Get the actions available for the resource.
      *
      * @param  \Illuminate\Http\Request  $request
-     *
      * @return array
      */
     public function actions(Request $request)