docs: @OverrideOnDemand
    protected void addMetaElements (@Nonnull final IRequestWebScopeWithoutResponse aRequestScope,
                                    @Nonnull final HCHead aHead)
    {
      final ICommonsList <IMetaElement> aMetaElements = new CommonsArrayList <> ();
      {
        // add special meta element at the beginning
        final IMimeType aMimeType = PhotonHTMLHelper.getMimeType (aRequestScope);
        aMetaElements.add (EStandardMetaElement.CONTENT_TYPE.getAsMetaElement (aMimeType.getAsString ()));
      }
      PhotonMetaElements.getAllRegisteredMetaElementsForGlobal (aMetaElements);
      PhotonMetaElements.getAllRegisteredMetaElementsForThisRequest (aMetaElements);
  
      for (final IMetaElement aMetaElement : aMetaElements)
        for (final Map.Entry <Locale, String> aEntry : aMetaElement.getContent ())
        {
          final HCMeta aMeta = new HCMeta ();
          if (aMetaElement.isHttpEquiv ())
            aMeta.setHttpEquiv (aMetaElement.getName ());
          else
            aMeta.setName (aMetaElement.getName ());
  
          aMeta.setContent (aEntry.getValue ());
  
          final Locale aContentLocale = aEntry.getKey ();
          if (aContentLocale != null && !LocaleHelper.isSpecialLocale (aContentLocale))
            aMeta.setLanguage (aContentLocale.toString ());
  
          aHead.metaElements ().add (aMeta);
        }
    }