Change Auditors to reuse Audit objects after persist

...va/edu/kit/scc/webreg/dao/jpa/audit/JpaAuditEntryDao.java

...ava/edu/kit/scc/webreg/entity/audit/AuditEntryEntity.java

...c/main/java/edu/kit/scc/webreg/audit/AbstractAuditor.java

...c/main/java/edu/kit/scc/webreg/audit/ApprovalAuditor.java

...java/edu/kit/scc/webreg/audit/AttributeSourceAuditor.java

...rvice/src/main/java/edu/kit/scc/webreg/audit/Auditor.java

.../src/main/java/edu/kit/scc/webreg/audit/GroupAuditor.java

...ava/edu/kit/scc/webreg/audit/IdpCommunicationAuditor.java

...c/main/java/edu/kit/scc/webreg/audit/RegistryAuditor.java

...rc/main/java/edu/kit/scc/webreg/audit/ServiceAuditor.java

...java/edu/kit/scc/webreg/audit/ServiceRegisterAuditor.java

...main/java/edu/kit/scc/webreg/audit/UserCreateAuditor.java

...main/java/edu/kit/scc/webreg/audit/UserUpdateAuditor.java

.../scc/webreg/service/reg/impl/RegisterUserServiceImpl.java