Timesheet validator: prevent overbooking budgets (#2422)

src/Timesheet/RateServiceInterface.php

@@ -0,0 +1,20 @@
+<?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\Timesheet;
+
+use App\Entity\Timesheet;
+
+/**
+ * Implementation to calculate the rate for a timesheet record.
+ */
+interface RateServiceInterface
+{
+    public function calculate(Timesheet $record): Rate;
+}