code: public static <T> Mapping<T> ignored(T instead) {
          String mname = "ignored to " + instead;
          return new FieldMapping<>(
                  InputMode.POLYMORPHIC,
                  ((name, data) -> instead),
                  new MappingMeta(mname, instead.getClass())
              ).options(o -> o._ignoreConstraints(true));
          }
docs: (mapping) ignore input value(s), and return 'instead' value
  NOTE: all constraints added to the outer 'ignored' mapping, will be ignored
  @param instead the value to be used
  @param <T> base type
  @return new created mapping