docs: private static Optional<String> roleNotLinkedToRelation(Role role, RelationType relationType, Relation relation) {
          boolean notFound = role.relations().
                  noneMatch(innerRelationType -> innerRelationType.label().equals(relationType.label()));
          if (notFound) {
              return Optional.of(VALIDATION_RELATION_CASTING_LOOP_FAIL.getMessage(relation.id(), role.label(), relationType.label()));
          }
          return Optional.empty();
      }