SimBrief integration #405 (#635)

* SimBrief integration #405

* Add briefing as API response; add acars_xml field #405

app/Contracts/Resource.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Contracts;
+
+/**
+ * Base class for a resource/response
+ */
+class Resource extends \Illuminate\Http\Resources\Json\Resource
+{
+    /**
+     * Iterate through the list of $fields and check if they're a "Unit"
+     * If they are, then add the response
+     *
+     * @param       $response
+     * @param array $fields
+     */
+    public function checkUnitFields(&$response, array $fields): void
+    {
+        foreach ($fields as $f) {
+            if ($this->{$f} instanceof Unit) {
+                $response[$f] = $this->{$f}->getResponseUnits();
+            } else {
+                $response[$f] = $this->{$f};
+            }
+        }
+    }
+}