docs: protected RuntimeConfig buildConfiguration(ServletContext servletContext,
                                                 ExternalContext externalContext, ExpressionFactory expressionFactory)
      {
          RuntimeConfig runtimeConfig = RuntimeConfig.getCurrentInstance(externalContext);
          runtimeConfig.setExpressionFactory(expressionFactory);
  
          // And configure everything
          new FacesConfigurator(externalContext).configure();
  
          validateFacesConfig(servletContext, externalContext);
  
          return runtimeConfig;
      }