Added more tests

...ice/api/src/main/java/at/tuwien/api/database/ViewDto.java

.../java/at/tuwien/api/database/table/columns/ColumnDto.java

...ice/src/main/java/at/tuwien/endpoints/AccessEndpoint.java

...e/src/main/java/at/tuwien/endpoints/DatabaseEndpoint.java

...vice/src/main/java/at/tuwien/endpoints/TableEndpoint.java

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

.../java/at/tuwien/endpoints/IdentifierEndpointUnitTest.java

.../test/java/at/tuwien/endpoints/TableEndpointUnitTest.java

...ava/at/tuwien/service/DatabaseServicePersistenceTest.java

...t/java/at/tuwien/validator/EndpointValidatorUnitTest.java

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

...rvice/rest-service/src/test/resources/json/metadata7.json

...main/java/at/tuwien/service/impl/DatabaseServiceImpl.java

...a-service/test/src/main/java/at/tuwien/test/BaseTest.java