docs: @Handler
      public void onRequestCompleted(
              Request.In.Completed event, IOSubchannel appChannel)
              throws InterruptedException {
          final Request.In requestEvent = event.event();
          // A check that also works with null.
          if (Boolean.TRUE.equals(requestEvent.get())
              || requestEvent.httpRequest().response().map(
                  response -> response.statusCode() != HttpStatus.NOT_IMPLEMENTED
                      .statusCode())
                  .orElse(false)) {
              // Some other component has taken care
              return;
          }
  
          // Check if "Not Found" should be sent
          if (providedFallbacks != null
              && providedFallbacks.contains(requestEvent.getClass())) {
              ResponseCreationSupport.sendResponse(
                  requestEvent.httpRequest(), appChannel, HttpStatus.NOT_FOUND);
              return;
          }
  
          // Last resort
          ResponseCreationSupport.sendResponse(requestEvent.httpRequest(),
              appChannel, HttpStatus.NOT_IMPLEMENTED);
      }