Add all files

app/Http/Resources/InvoiceResource.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Resources;
+
+use TiMacDonald\JsonApi\JsonApiResource;
+
+/**
+ * @mixin \App\Models\Invoice
+ */
+class InvoiceResource extends JsonApiResource
+{
+    public $attributes = [
+        'id',
+        'status',
+        'currency_code',
+        'due_at',
+        'updated_at',
+        'created_at',
+    ];
+
+    public $relationships = [
+        'user' => UserResource::class,
+        'items' => InvoiceItemResource::class,
+    ];
+}