### 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 throwOnCopyToOnObject(Mapper mapper, List<String> copyToFields, DocumentParserContext context) {
        throw new DocumentParsingException(
            context.parser().getTokenLocation(),
            "Cannot copy field ["
                + mapper.name()
                + "] to fields "
                + copyToFields
                + ". Copy-to currently only works for value-type fields, not objects."
        );
    }
    private static void parseObject(final DocumentParserContext context, String currentFieldName) throws IOException {
        assert currentFieldName != null;
        Mapper objectMapper = context.getMapper(currentFieldName);
        if (objectMapper != null) {
            context.path().add(currentFieldName);
            if (objectMapper instanceof ObjectMapper objMapper) {
                if (objMapper.subobjects() == false) {
                    context.path().setWithinLeafObject(true);
                }
            }
            parseObjectOrField(context, objectMapper);
            context.path().setWithinLeafObject(false);
            context.path().remove();
        } else {
            parseObjectDynamic(context, currentFieldName);
        }
    }
    private static void parseObjectDynamic(DocumentParserContext context, String currentFieldName) throws IOException {
        if (context.dynamic() == ObjectMapper.Dynamic.STRICT) {