Add all files

app/Http/Resources/InvoiceItemResource.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Http\Resources;
+
+use TiMacDonald\JsonApi\JsonApiResource;
+
+class InvoiceItemResource extends JsonApiResource
+{
+    public $attributes = [
+        'id',
+        'quantity',
+        'price',
+        'currency_code',
+        'expires_at',
+        'updated_at',
+        'created_at',
+    ];
+
+    public $relationships = [
+        'services' => ServiceResource::class,
+        'invoice' => InvoiceResource::class,
+    ];
+}