code: protected I_CmsSearchDocument appendFieldMapping(
          I_CmsSearchDocument document,
          CmsSearchField field,
          CmsObject cms,
          CmsResource resource,
          I_CmsExtractionResult extractionResult,
          List<CmsProperty> properties,
          List<CmsProperty> propertiesSearched) {
  
          StringBuffer text = new StringBuffer();
          for (I_CmsSearchFieldMapping mapping : field.getMappings()) {
              String mapResult = mapping.getStringValue(cms, resource, extractionResult, properties, propertiesSearched);
              if (mapResult != null) {
                  if (text.length() > 0) {
                      text.append('\n');
                  }
                  text.append(mapResult);
              }
          }
          if (text.length() > 0) {
              document.addSearchField(field, text.toString());
          }
  
          return document;
      }
docs: Extends the given document by the mappings for the given field.<p>
  
  @param document the document to extend
  @param field the field to create the mappings for
  @param cms the OpenCms context used for building the search index
  @param resource the resource that is indexed
  @param extractionResult the plain text extraction result from the resource
  @param properties the list of all properties directly attached to the resource (not searched)
  @param propertiesSearched the list of all searched properties of the resource
  
  @return the document extended by the mappings for the given field