Fixed various front-end related bugs

dbrepo-authentication-service/dbrepo-realm.json

...main/java/at/tuwien/api/database/table/TableBriefDto.java

.../src/main/java/at/tuwien/api/database/table/TableDto.java

...in/java/at/tuwien/api/identifier/IdentifierCreateDto.java

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

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

...b/api/src/main/java/at/tuwien/api/user/UserUpdateDto.java

...rc/main/java/at/tuwien/entities/database/table/Table.java

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

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

.../entities/src/main/java/at/tuwien/entities/user/Role.java

...es/src/main/java/at/tuwien/entities/user/RoleMapping.java

.../entities/src/main/java/at/tuwien/entities/user/User.java

dbrepo-metadata-db/setup-schema.sql

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

dbrepo-proxy/dbrepo.conf

...rvice/src/main/java/at/tuwien/endpoint/QueryEndpoint.java

...rvice/src/main/java/at/tuwien/endpoint/StoreEndpoint.java

...e/src/main/java/at/tuwien/endpoint/TableDataEndpoint.java

...src/main/java/at/tuwien/validation/EndpointValidator.java