Invoices can be uploaded

app/Providers/FlashMessageProvider.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Providers;
+
+class FlashMessageProvider {
+    public function __construct(string $message, string $messageType) {
+        session()->put('message',
+            serialize(['messageType' => $messageType, 'message' => $message])
+        );
+    }
+}