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/DynamicFieldsBuilder.java
createDynamicStringFieldFromTemplate(context, name);
        }
    }
    /**
     * Returns a dynamically created object mapper, eventually based on a matching dynamic template.
     */
    static Mapper createDynamicObjectMapper(DocumentParserContext context, String name) {
        Mapper mapper = createObjectMapperFromTemplate(context, name);
        return mapper != null
            ? mapper
            : new ObjectMapper.Builder(name, ObjectMapper.Defaults.SUBOBJECTS).enabled(ObjectMapper.Defaults.ENABLED)
                .build(context.createDynamicMapperBuilderContext());
    }
    /**
     * Returns a dynamically created object mapper, based exclusively on a matching dynamic template, null otherwise.
     */
    static Mapper createObjectMapperFromTemplate(DocumentParserContext context, String name) {
        Mapper.Builder templateBuilder = findTemplateBuilderForObject(context, name);
        return templateBuilder == null ? null : templateBuilder.build(context.createDynamicMapperBuilderContext());
    }
    /**
     * Creates a dynamic string field based on a matching dynamic template.
     * No field is created in case there is no matching dynamic template.
     */
    static void createDynamicStringFieldFromTemplate(DocumentParserContext context, String name) throws IOException {
        createDynamicField(context, name, DynamicTemplate.XContentFieldType.STRING, () -> {});
    }
    private static void createDynamicDateField(
        DocumentParserContext context,
        String name,