code: private JsfFaceletDescriptor getJsfTemplateDescriptor(String fullFilePath, ScannerContext context) {
          // can't handle EL-expressions
          if (isElExpression(fullFilePath)) {
              return null;
          }
          return context.peek(FileResolver.class).require(fullFilePath, JsfFaceletDescriptor.class, context);
      }
docs: Tries to find a {@link JsfFaceletDescriptor} in the store with the given
  fullFilePath. Creates a new one if no descriptor could be found.
  
  @param fullFilePath
  the file path of the wanted file
  @param context
  The scanner context.
  @return a {@link JsfFaceletDescriptor} representing the wanted file