OZG-6240 Rename to XtaIdentifier

src/main/java/de/ozgcloud/xta/client/XtaClient.java

...n/java/de/ozgcloud/xta/client/config/XtaClientConfig.java

...n/java/de/ozgcloud/xta/client/core/WrappedXtaService.java

...ain/java/de/ozgcloud/xta/client/mapper/RequestMapper.java

...in/java/de/ozgcloud/xta/client/mapper/ResponseMapper.java

...main/java/de/ozgcloud/xta/client/model/XtaIdentifier.java

...java/de/ozgcloud/xta/client/model/XtaMessageMetaData.java

...va/de/ozgcloud/xta/client/XtaDevServerSetupExtension.java

.../java/de/ozgcloud/xta/client/XtaMessageExampleLoader.java

...a/de/ozgcloud/xta/client/XtaTestServerSetupExtension.java

...gcloud/xta/client/factory/MessageMetaDataTestFactory.java

...gcloud/xta/client/factory/XtaClientConfigTestFactory.java