Fixed some tests and removed the visibility setting as it is not needed

dbrepo-authentication-service/dbrepo-realm.json

...src/main/java/at/tuwien/endpoints/IdentifierEndpoint.java

...rc/main/java/at/tuwien/endpoints/PersistenceEndpoint.java

...t/java/at/tuwien/endpoint/IdentifierEndpointUnitTest.java

.../java/at/tuwien/endpoint/PersistenceEndpointUnitTest.java

...est/java/at/tuwien/service/IdentifierServiceUnitTest.java

...rvice/rest-service/src/test/resources/json/metadata0.json

...rvice/rest-service/src/test/resources/json/metadata1.json

...in/java/at/tuwien/service/impl/IdentifierServiceImpl.java

...src/main/java/at/tuwien/api/identifier/IdentifierDto.java

...main/java/at/tuwien/api/identifier/VisibilityTypeDto.java

...c/main/java/at/tuwien/entities/identifier/Identifier.java

...in/java/at/tuwien/entities/identifier/VisibilityType.java

dbrepo-metadata-db/setup-schema.sql

...tadata-db/test/src/main/java/at/tuwien/test/BaseTest.java