Added not allowed exception, mistook the sequence name

...a/at/tuwien/service/IdentifierServiceIntegrationTest.java

...s/src/main/java/at/tuwien/entities/database/Database.java

.../src/main/java/at/tuwien/entities/identifier/Creator.java

fda-metadata-db/setup-schema.sql

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

...rc/main/java/at/tuwien/exception/NotAllowedException.java