### 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
DocumentLeafReader reader = new DocumentLeafReader(context.rootDoc(), fieldScripts);
        for (Consumer<LeafReaderContext> script : fieldScripts.values()) {
            script.accept(reader.getContext());
        }
    }
    private static void validateStart(XContentParser parser) throws IOException {
        
        XContentParser.Token token = parser.nextToken();
        if (token != XContentParser.Token.START_OBJECT) {
            throwNoStartOnObject();
        }
    }
    private static void throwNoStartOnObject() {
        throw new DocumentParsingException(XContentLocation.UNKNOWN, "Malformed content, must start with an object");
    }
    private static void validateEnd(XContentParser parser) throws IOException {
        XContentParser.Token token;
        
        
        token = parser.nextToken();
        if (token != null) {
            throwNotAtEnd(token);
        }
    }
    private static void throwNotAtEnd(XContentParser.Token token) {
        throw new IllegalArgumentException("Malformed content, found extra data after parsing: " + token);
    }
    private static boolean isEmptyDoc(RootObjectMapper root, XContentParser parser) throws IOException {
        if (root.isEnabled()) {
            final XContentParser.Token token = parser.nextToken();