added annotation based exporter (#1831)

* added user exporter
* added project exporter
* added customer exporter
* added activity exporter

src/Export/Spreadsheet/AnnotatedObjectExporter.php

@@ -0,0 +1,32 @@
+<?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\Export\Spreadsheet;
+
+use App\Export\Spreadsheet\Extractor\AnnotationExtractor;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+
+final class AnnotatedObjectExporter
+{
+    private $spreadsheetExporter;
+    private $annotationExtractor;
+
+    public function __construct(SpreadsheetExporter $spreadsheetExporter, AnnotationExtractor $annotationExtractor)
+    {
+        $this->spreadsheetExporter = $spreadsheetExporter;
+        $this->annotationExtractor = $annotationExtractor;
+    }
+
+    public function export(string $class, array $entries): Spreadsheet
+    {
+        $columns = $this->annotationExtractor->extract($class);
+
+        return $this->spreadsheetExporter->export($columns, $entries);
+    }
+}