Make sorting of invoice items reliable.

app/Http/Controllers/Api/InvoiceitemController.php

@@ -32,7 +32,7 @@ class InvoiceitemController extends Controller
             'name' => 'required|string',
             'description' => 'nullable|string',
             'article_number' => 'nullable|string',
-
+            'sort' => 'required|numeric|min:0',
         ]);
 
         $item = $invoice->items()->create($itemData);

app/Models/Invoice.php

@@ -104,7 +104,7 @@ class Invoice extends Model
      */
     public function items(): HasMany
     {
-        return $this->hasMany(Invoiceitem::class);
+        return $this->hasMany(Invoiceitem::class)->orderBy('sort');
     }
 
     /**

app/Models/Invoiceitem.php

@@ -22,6 +22,7 @@ class Invoiceitem extends Model
         'total',
         'name',
         'description',
+        'sort'
     ];
 
 }