added API for handling work contract times (#4016)

tests/Model/DayTest.php

@@ -0,0 +1,26 @@
+<?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\Model;
+
+use App\Model\Day;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \App\Model\Day
+ */
+class DayTest extends TestCase
+{
+    public function testDefaults(): void
+    {
+        $date = new \DateTimeImmutable('2023-07-21');
+        $sut = new Day($date);
+        self::assertSame($date, $sut->getDay());
+    }
+}