Notifications: added user preference UI & logic

Includes testing to cover.
Also added file missing from previous commit.

app/Settings/UserNotificationPreferences.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace BookStack\Settings;
+
+use BookStack\Users\Models\User;
+
+class UserNotificationPreferences
+{
+    public function __construct(
+        protected User $user
+    ) {
+    }
+
+    public function notifyOnOwnPageChanges(): bool
+    {
+        return $this->getNotificationSetting('own-page-changes');
+    }
+
+    public function notifyOnOwnPageComments(): bool
+    {
+        return $this->getNotificationSetting('own-page-comments');
+    }
+
+    public function notifyOnCommentReplies(): bool
+    {
+        return $this->getNotificationSetting('comment-replies');
+    }
+
+    public function updateFromSettingsArray(array $settings)
+    {
+        $allowList = ['own-page-changes', 'own-page-comments', 'comment-replies'];
+        foreach ($settings as $setting => $status) {
+            if (!in_array($setting, $allowList)) {
+                continue;
+            }
+
+            $value = $status === 'true' ? 'true' : 'false';
+            setting()->putUser($this->user, 'notifications#' . $setting, $value);
+        }
+    }
+
+    protected function getNotificationSetting(string $key): bool
+    {
+        return setting()->getUser($this->user, 'notifications#' . $key);
+    }
+}