Release 2.0.9 (#3922)

* fix api definition
* include customer number in validation message
* fix doctrine deprecation, prepare for DBAL 4
* added DataSubscriberInterface to identify certain doctrine subscribers

migrations/Version20210802152814.php

@@ -51,7 +51,7 @@ final class Version20210802152814 extends AbstractMigration
     public function down(Schema $schema): void
     {
         $timesheet = $schema->getTable('kimai2_timesheet');
-        $timesheet->changeColumn('date_tz', ['notnull' => false]);
+        $timesheet->modifyColumn('date_tz', ['notnull' => false]);
 
         $this->preventEmptyMigrationWarning();
     }