added csv importer for timesheet and project data (#1216)

src/Importer/InvalidFieldsException.php

@@ -0,0 +1,28 @@
+<?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\Importer;
+
+use Throwable;
+
+class InvalidFieldsException extends \Exception
+{
+    private $fields = [];
+
+    public function __construct(array $fields, $code = 0, Throwable $previous = null)
+    {
+        parent::__construct(sprintf('Missing fields: %s', implode(', ', $fields)), $code, $previous);
+        $this->fields = $fields;
+    }
+
+    public function getFields(): array
+    {
+        return $this->fields;
+    }
+}