code: private ResourceModelSource createCachingSource(
              ResourceModelSource origin,
              String ident,
              String descr
      )
      {
          return createCachingSource(origin, ident, descr, SourceFactory.CacheType.BOTH, true);
      }
docs: @param origin origin source
  @param ident  unique identity for this cached source, used in filename
  @param descr  description of the source, used in logging
  
  @return new source