### 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/DocumentParserContext.java
@Override
            public boolean isWithinCopyTo() {
                return true;
            }
            @Override
            public LuceneDocument doc() {
                return doc;
            }
        };
    }
    /**
     * Return a context for flattening subobjects
     * @param fieldName   the name of the field to be flattened
     */
    public final DocumentParserContext createFlattenContext(String fieldName) {
        XContentParser flatteningParser = new FlatteningXContentParser(parser(), fieldName);
        return new Wrapper(this.parent(), this) {
            @Override
            public XContentParser parser() {
                return flatteningParser;
            }
        };
    }
    /**
     *  @deprecated we are actively deprecating and removing the ability to pass
     *              complex objects to multifields, so try and avoid using this method
     * Replace the XContentParser used by this context
     * @param parser    the replacement parser
     * @return  a new context with a replaced parser
     */