docs: @Override
      public CacheKey getCacheKey(HttpServletRequest request, HttpServletResponse response) {
          final CacheKeyBuilder cacheKeyBuilder = CacheKey.builder(this.getClass().getName());
  
          for (final TransformerConfigurationSource source : this.sources) {
              final CacheKey key = source.getCacheKey(request, response);
              cacheKeyBuilder.add(key);
          }
  
          return cacheKeyBuilder.build();
      }