The `ignore_malformed` option is supported by a few of our field types, mainly numerics and dates, to still accept the document when such fields hold malformed values. See https://www.elastic.co/guide/en/elasticsearch/reference/current/ignore-malformed.html. Also `ignore_malformed` is an index level setting that gets applied to all field types that support it. 

The boolean field type does not support `ignore_malformed` but it should, so that if a boolean field cannot be parsed as a boolean, the document can still be accepted.


server/src/main/java/org/elasticsearch/index/mapper/BooleanFieldMapper.java
String textValue = value.toString();
                        return Booleans.parseBoolean(textValue.toCharArray(), 0, textValue.length(), false);
                    }
                }
            };
        }
        @Override
        public BytesRef indexedValueForSearch(Object value) {
            if (value == null) {
                return Values.FALSE;
            }
            if (value instanceof Boolean) {
                return ((Boolean) value) ? Values.TRUE : Values.FALSE;
            }
            String sValue;
            if (value instanceof BytesRef) {
                sValue = ((BytesRef) value).utf8ToString();
            } else {
                sValue = value.toString();
            }
            return switch (sValue) {
                case "true" -> Values.TRUE;
                case "false" -> Values.FALSE;
                default -> throw new IllegalArgumentException("Can't parse boolean value [" + sValue + "], expected [true] or [false]");
            };
        }
        private long docValueForSearch(Object value) {
            BytesRef ref = indexedValueForSearch(value);
            if (Values.TRUE.equals(ref)) {
                return 1;