code: public void doRuntimeConfiguration(RuntimeSpringConfiguration springConfig) {
          ApplicationContext context = springConfig.getUnrefreshedApplicationContext();
          AutowireCapableBeanFactory autowireCapableBeanFactory = context.getAutowireCapableBeanFactory();
          if(autowireCapableBeanFactory instanceof ConfigurableListableBeanFactory) {
              ConfigurableListableBeanFactory beanFactory = (ConfigurableListableBeanFactory)autowireCapableBeanFactory;
              ConversionService existingConversionService = beanFactory.getConversionService();
              ConverterRegistry converterRegistry;
              if(existingConversionService == null) {
                  GenericConversionService conversionService = new GenericConversionService();
                  converterRegistry = conversionService;
                  beanFactory.setConversionService(conversionService);
              }
              else {
                  converterRegistry = (ConverterRegistry)existingConversionService;
              }
  
              converterRegistry.addConverter(new Converter<NavigableMap.NullSafeNavigator, Object>() {
                  @Override
                  public Object convert(NavigableMap.NullSafeNavigator source) {
                      return null;
                  }
              });
          }
          checkInitialised();
          for (GrailsPlugin plugin : pluginList) {
              if (plugin.supportsCurrentScopeAndEnvironment() && plugin.isEnabled(context.getEnvironment().getActiveProfiles())) {
                  plugin.doWithRuntimeConfiguration(springConfig);
              }
          }
      }
docs: Base implementation that simply goes through the list of plugins and calls doWithRuntimeConfiguration on each
  @param springConfig The RuntimeSpringConfiguration instance