Extract customer creation/cleanup

This also ensures that cleanup always runs after all integration tests

MAILPOET-5145

mailpoet/tests/integration/API/JSON/v1/SetupTest.php

@@ -57,6 +57,7 @@ class SetupTest extends \MailPoetTest {
   }
 
   public function _after() {
+    parent::_after();
     $this->diContainer->get(SettingsRepository::class)->truncate();
   }
 }