bugfixes (#3078)

* fix phpdoc
* fix invoice export field order
* prevent empty migration warning
* do not trigger export validation on new timesheets
* update license year
* remove trailing comma in function call for php compatibility
* add new composer plugin config
* bump phpunit schema version

src/Migrations/Version20211008092010.php

@@ -38,5 +38,7 @@ final class Version20211008092010 extends AbstractMigration
         $projects = $schema->getTable('kimai2_projects');
         $column = $projects->getColumn('order_number');
         $column->setOptions(['length' => 20]);
+
+        $this->preventEmptyMigrationWarning();
     }
 }