OZG-7037 apply more code review comments

...va/de/ozgcloud/archive/common/command/CommandService.java

...ava/de/ozgcloud/archive/vorgang/ArchiveEventListener.java

...main/java/de/ozgcloud/archive/vorgang/VorgangService.java

...e/ozgcloud/archive/common/command/CommandServiceTest.java

...hive/common/xta/JsonToXtaIdentifierListConverterTest.java

...ozgcloud/archive/common/xta/XtaIdentifierTestFactory.java

...t/java/de/ozgcloud/archive/common/xta/XtaServiceTest.java

...a/de/ozgcloud/archive/export/ExportGrpcServiceITCase.java

...st/java/de/ozgcloud/archive/export/ExportServiceTest.java

...zgcloud/archive/export/XdomeaPropertiesValidatorTest.java

...de/ozgcloud/archive/vorgang/ArchiveEventListenerTest.java

...est/java/de/ozgcloud/archive/vorgang/KopfCreatorTest.java

.../java/de/ozgcloud/archive/vorgang/VorgangServiceTest.java