### 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
LuceneDocument targetDoc = null;
            for (LuceneDocument doc = context.doc(); doc != null; doc = doc.getParent()) {
                if (field.startsWith(doc.getPrefix())) {
                    targetDoc = doc;
                    break;
                }
            }
            assert targetDoc != null;
            final DocumentParserContext copyToContext = context.createCopyToContext(field, targetDoc);
            innerParseObject(copyToContext);
        }
    }
    
    
    
    private static Mapper getLeafMapper(final DocumentParserContext context, String fieldName) {
        Mapper mapper = context.getMapper(fieldName);
        if (mapper != null) {
            return mapper;
        }
        
        
        
        String fieldPath = context.path().pathAsText(fieldName);
        MappedFieldType fieldType = context.mappingLookup().getFieldType(fieldPath);
        if (fieldType != null) {
            
            assert fieldType.hasDocValues() == false && fieldType.isAggregatable() && fieldType.isSearchable();