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
public static final String CONTENT_TYPE = "boolean";
    public static class Defaults {
        public static final FieldType FIELD_TYPE = new FieldType();
        static {
            FIELD_TYPE.setOmitNorms(true);
            FIELD_TYPE.setIndexOptions(IndexOptions.DOCS);
            FIELD_TYPE.setTokenized(false);
            FIELD_TYPE.freeze();
        }
    }
    public static class Values {
        public static final BytesRef TRUE = new BytesRef("T");
        public static final BytesRef FALSE = new BytesRef("F");
    }
    private static BooleanFieldMapper toType(FieldMapper in) {
        return (BooleanFieldMapper) in;
    }
    public static class Builder extends FieldMapper.Builder {