code: public HalResource renameEmbedded(String relToRename, String newRel) {
      List<HalResource> resources = getEmbedded(relToRename);
      return removeEmbedded(relToRename).addEmbedded(newRel, resources);
    }
docs: Changes the rel of embedded resources
  @param relToRename the rel that you want to change
  @param newRel the new rel for all embedded items
  @return HAL resource