Current state

app/Models/ContentType.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+class ContentType extends Model
+{
+    protected $fillable = ['name','slug','description'];
+
+    public function categories(): HasMany
+    {
+        return $this->hasMany(Category::class);
+    }
+
+    public function rootCategories(): HasMany
+    {
+        return $this->categories()->whereNull('parent_id');
+    }
+
+    public function getRouteKeyName(): string
+    {
+        return 'slug';
+    }
+}