code: @Override
      public OptionalThing<ApiResponse> handleClientException(ApiFailureResource resource, RuntimeException cause) {
          final FaihyUnifiedFailureType failureType = FaihyUnifiedFailureType.CLIENT_ERROR;
          final FaihyUnifiedFailureResult result = createFailureResult(failureType, resource, cause);
          adjustClientExceptionErrors(resource, cause, result);
          return OptionalThing.of(asJson(result)); // HTTP status will be automatically sent as client error for the cause
      }
docs: ----------------