code: protected function execute(InputInterface $input, OutputInterface $output)
      {
          $appFqcn = $input->getArgument('app');
  
          if (! class_exists($appFqcn)) {
              throw new \InvalidArgumentException("Class not found: $appFqcn");
          }
  
          if (! is_a($appFqcn, AviatorApp::class, true)) {
              throw new \InvalidArgumentException('The app class must implement ' . AviatorApp::class);
          }
  
          $app = new $appFqcn($this->environment);
  
          $builder = new BootingAppBuilder();
          $builder->doFullBootBuild($app);
  
          $output->writeln('Successfully built app ' . $appFqcn);
  
          return 0;
      }
docs: @param InputInterface  $input
  @param OutputInterface $output
  
  @return mixed