static O[] params_plusHTMLClass(MapSO params, S className) {
  ret params_plusHTMLClass(wrapMapAsParams(params), className);
}

static O[] params_plusHTMLClass(O[] params, S className) {
  if (empty(className)) ret params;
  ret paramsPlus(params, class := joinNemptiesWithSpace(stringPar("class", params), className));
}

static O[] params_plusHTMLClass(S className, O[] params) {
  ret params_plusHTMLClass(params, className);
}

Began life as a copy of #1024480