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/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java
}
            private Tuple<Boolean, Boolean> generateValue() {
                if (nullValue != null && randomBoolean()) {
                    return Tuple.tuple(null, nullValue);
                }
                boolean b = randomBoolean();
                return Tuple.tuple(b, b);
            }
            private void mapping(XContentBuilder b) throws IOException {
                minimalMapping(b);
                if (nullValue != null) {
                    b.field("null_value", nullValue);
                }
            }
            @Override
            public List<SyntheticSourceInvalidExample> invalidExample() throws IOException {
                return List.of(
                    new SyntheticSourceInvalidExample(
                        equalTo("field [field] of type [boolean] doesn't support synthetic source because it doesn't have doc values"),
                        b -> b.field("type", "boolean").field("doc_values", false)
                    )
                
                );
            }
        };
    }
    protected IngestScriptSupport ingestScriptSupport() {
        return new IngestScriptSupport() {
            @Override
            protected BooleanFieldScript.Factory emptyFieldScript() {