private static HttpResponse newFallbackResponse(ServiceRequestContext ctx, HttpStatus status) {
        final ServiceErrorHandler errorHandler = ctx.config().errorHandler();
        final AggregatedHttpResponse rendered = errorHandler.renderStatus(ctx,
                                                                          ctx.request().headers(),
                                                                          status,
                                                                          null,
                                                                          null);
        if (rendered != null) {
            return rendered.toHttpResponse();
        }
        return HttpResponse.of(ResponseHeaders.builder(status)
                                              .endOfStream(true)
                                              .build());
    }
Handles the {@link HttpRequest}s that are not matched by any user-specified {@link Route}s.
core/src/main/java/com/linecorp/armeria/server/FallbackService.java