(add basic tests for viewing published concert orders page)

app/Http/Controllers/Backstage/PublishedConcertOrdersController.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace App\Http\Controllers\Backstage;
+
+use Illuminate\Http\Request;
+use App\Http\Controllers\Controller;
+use Illuminate\Support\Facades\Auth;
+
+class PublishedConcertOrdersController extends Controller
+{
+    public function index($concertId)
+    {
+        $concert = Auth::user()->concerts()->published()->findOrFail($concertId);
+
+        return view('backstage.published-concert-orders.index', [
+            'concert' => $concert,
+        ]);
+    }
+}