Add Notification Type Extender and Tests (#2424)

src/Extend/Notification.php

@@ -0,0 +1,38 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Extend;
+
+use Flarum\Extension\Extension;
+use Illuminate\Contracts\Container\Container;
+
+class Notification implements ExtenderInterface
+{
+    private $blueprints = [];
+    private $serializers = [];
+
+    public function type(string $blueprint, string $serializer, array $channelsEnabledByDefault = [])
+    {
+        $this->blueprints[$blueprint] = $channelsEnabledByDefault;
+        $this->serializers[$blueprint::getType()] = $serializer;
+
+        return $this;
+    }
+
+    public function extend(Container $container, Extension $extension = null)
+    {
+        $container->extend('flarum.notification.blueprints', function ($existingBlueprints) {
+            return array_merge($existingBlueprints, $this->blueprints);
+        });
+
+        $container->extend('flarum.api.notification_serializers', function ($existingSerializers) {
+            return array_merge($existingSerializers, $this->serializers);
+        });
+    }
+}