OZG-6177 refactor service class

Jenkinsfile

pom.xml

...ertransfer/user/OzgCloudElsterTransferUserReconciler.java

...lstertransfer/user/OzgCloudElsterTransferUserService.java

...rtransfer/user/OzgCloudElsterTransferUserServiceTest.java

src/test/resources/users.tmpl