Update some APIs

- Rename DiscussionSearchWillBePerformed to ConfigureDiscussionSearch, same with users
- Add some handy methods

src/Event/ConfigureUserSearch.php

@@ -0,0 +1,37 @@
+<?php
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Event;
+
+use Flarum\Core\Search\User\UserSearch;
+use Flarum\Core\Search\SearchCriteria;
+
+class ConfigureUserSearch
+{
+    /**
+     * @var UserSearch
+     */
+    public $search;
+
+    /**
+     * @var SearchCriteria
+     */
+    public $criteria;
+
+    /**
+     * @param UserSearch $search
+     * @param SearchCriteria $criteria
+     */
+    public function __construct(UserSearch $search, SearchCriteria $criteria)
+    {
+        $this->search = $search;
+        $this->criteria = $criteria;
+    }
+}