### Description

Dynamic mappings can greatly help the getting started experience but they currently don't apply to all types, one example is `dense_vector`.

It's been suggested to automatically map float arrays as dense vectors when there are more than 100 values, or a heuristic along these lines.
server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java
}
    private static void parseValue(final DocumentParserContext context, String currentFieldName) throws IOException {
        if (currentFieldName == null) {
            throwOnNoFieldName(context);
        }
        Mapper mapper = getLeafMapper(context, currentFieldName);
        if (mapper != null) {
            parseObjectOrField(context, mapper);
        } else {
            parseDynamicValue(context, currentFieldName);
        }
    }
    private static void throwOnNoFieldName(DocumentParserContext context) throws IOException {
        throw new DocumentParsingException(
            context.parser().getTokenLocation(),
            "object mapping ["
                + context.parent().name()
                + "] trying to serialize a value with"
                + " no field associated with it, current value ["
                + context.parser().textOrNull()
                + "]"
        );
    }
    private static void parseNullValue(DocumentParserContext context, String lastFieldName) throws IOException {
        
        Mapper mapper = getLeafMapper(context, lastFieldName);
        if (mapper != null) {
            
            parseObjectOrField(context, mapper);
        } else if (context.dynamic() == ObjectMapper.Dynamic.STRICT) {