docs: private void setUpDefaultUriComboBox(List<CmsSite> allSites) {
  
          BeanItemContainer<CmsSite> objects = new BeanItemContainer<CmsSite>(CmsSite.class, allSites);
          m_fieldDefaultURI.setContainerDataSource(objects);
          m_fieldDefaultURI.setNullSelectionAllowed(false);
          m_fieldDefaultURI.setTextInputAllowed(false);
          m_fieldDefaultURI.setItemCaptionPropertyId("title");
  
          //set value
          String siteRoot = OpenCms.getSiteManager().getDefaultUri();
          if (siteRoot.endsWith("/")) {
              siteRoot = siteRoot.substring(0, siteRoot.length() - 1);
          }
          CmsSite site = OpenCms.getSiteManager().getSiteForSiteRoot(siteRoot);
          m_fieldDefaultURI.setValue(site);
      }