docs: protected boolean determineFeatureState(final ITemplateContext context, final IProcessableElementTag tag, final AttributeName attributeName, final String attributeValue, boolean defaultState) {
          final IStandardExpressionParser expressionParser = StandardExpressions.getExpressionParser(context.getConfiguration());
          final IStandardExpression expression = expressionParser.parseExpression(context, attributeValue);
          final Object value = expression.execute(context);
          if (value != null) {
              return isFeatureActive(value.toString());
          }
          else {
              return defaultState;
          }
      }