replaced mailer library, added email templates (#1462)

tests/Configuration/MailConfigurationTest.php

@@ -0,0 +1,33 @@
+<?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\Tests\Configuration;
+
+use App\Configuration\MailConfiguration;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \App\Configuration\MailConfiguration
+ */
+class MailConfigurationTest extends TestCase
+{
+    public function testGetFromAddress()
+    {
+        $previous = getenv('MAILER_FROM');
+        putenv('MAILER_FROM=foo-bar123@example.com');
+
+        $sut = new MailConfiguration();
+        self::assertEquals('foo-bar123@example.com', $sut->getFromAddress());
+
+        putenv('MAILER_FROM=');
+        self::assertNull($sut->getFromAddress());
+
+        putenv('MAILER_FROM=' . $previous);
+    }
+}