Edit the mail config from the dashboard and provide testing button

app/Bus/Handlers/Commands/System/Config/UpdateConfigCommandHandler.php

@@ -0,0 +1,68 @@
+<?php
+
+/*
+ * This file is part of Cachet.
+ *
+ * (c) Alt Three Services Limited
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace CachetHQ\Cachet\Bus\Handlers\Commands\System\Config;
+
+use Dotenv\Dotenv;
+use Dotenv\Exception\InvalidPathException;
+use CachetHQ\Cachet\Bus\Commands\System\Config\UpdateConfigCommand;
+
+/**
+ * This is the update config command handler class.
+ *
+ * @author James Brooks <james@alt-three.com>
+ */
+class UpdateConfigCommandHandler
+{
+    /**
+     * Handle update config command handler instance.
+     *
+     * @param \CachetHQ\Cachet\Bus\Commands\System\Config\UpdateConfigCommand $command
+     *
+     * @return void
+     */
+    public function handle(UpdateConfigCommand $command)
+    {
+        foreach ($command->values as $setting => $value) {
+            $this->writeEnv($setting, $value);
+        }
+    }
+
+    /**
+     * Writes to the .env file with given parameters.
+     *
+     * @param string $key
+     * @param mixed  $value
+     *
+     * @return void
+     */
+    protected function writeEnv($key, $value)
+    {
+        $dir = app()->environmentPath();
+        $file = app()->environmentFile();
+        $path = "{$dir}/{$file}";
+
+        try {
+            (new Dotenv($dir, $file))->load();
+
+            $envKey = strtoupper($key);
+            $envValue = env($envKey) ?: 'null';
+
+            file_put_contents($path, str_replace(
+                "{$envKey}={$envValue}",
+                "{$envKey}={$value}",
+                file_get_contents($path)
+            ));
+        } catch (InvalidPathException $e) {
+            throw $e;
+        }
+    }
+}