added database driven system configurations with admin screen (#647)

src/Event/SystemConfigurationEvent.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Event;
+
+use App\Form\Model\SystemConfiguration;
+use Symfony\Component\EventDispatcher\Event;
+
+/**
+ * This event should be used, if system configurations should be changed/added dynamically.
+ */
+class SystemConfigurationEvent extends Event
+{
+    public const CONFIGURE = 'app.system_configuration';
+
+    /**
+     * @var SystemConfiguration[]
+     */
+    protected $preferences;
+
+    /**
+     * @param SystemConfiguration[] $configurations
+     */
+    public function __construct(array $configurations)
+    {
+        $this->preferences = $configurations;
+    }
+
+    /**
+     * @return SystemConfiguration[]
+     */
+    public function getConfigurations()
+    {
+        return $this->preferences;
+    }
+
+    /**
+     * @param SystemConfiguration $configuration
+     * @return SystemConfigurationEvent
+     */
+    public function addConfiguration(SystemConfiguration $configuration): SystemConfigurationEvent
+    {
+        $this->preferences[] = $configuration;
+
+        return $this;
+    }
+}