better collection handlich in backend

app/Models/Collection.php

@@ -7,9 +7,34 @@ use App\Models\Dataset;
 
 class Collection extends Model
 {
+    public $timestamps = false;
+    protected $fillable = [
+        'name',
+        'role_id',
+    ];
 
     public function documents()
     {
         return $this->belongsToMany(Dataset::class, 'link_documents_collections', 'collection_id', 'document_id');
     }
+
+    #region self join
+    public function parent()
+    {
+        return $this->belongsTo(self::class, 'parent_id');
+    }
+
+    public function children()
+    {
+        return $this->hasMany(self::class, 'parent_id');
+    }
+    #endregion
+
+    /**
+     * Get the collection role that the dataset belongs to.
+     */
+    public function collectionrole()
+    {
+        return $this->belongsTo(CollectionRole::class, 'role_id', 'id');
+    }
 }