### 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
return;
                }
            }
            if (context.dynamic() != ObjectMapper.Dynamic.RUNTIME) {
                context.addDynamicMapper(dynamicObjectMapper);
            }
            if (dynamicObjectMapper instanceof NestedObjectMapper && context.isWithinCopyTo()) {
                throwOnCreateDynamicNestedViaCopyTo(dynamicObjectMapper, context);
            }
            context.path().add(currentFieldName);
            if (dynamicObjectMapper instanceof ObjectMapper objectMapper) {
                if (objectMapper.subobjects() == false) {
                    context.path().setWithinLeafObject(true);
                }
            }
            parseObjectOrField(context, dynamicObjectMapper);
            context.path().setWithinLeafObject(false);
            context.path().remove();
        }
    }
    private static void throwOnCreateDynamicNestedViaCopyTo(Mapper dynamicObjectMapper, DocumentParserContext context) {
        throw new DocumentParsingException(
            context.parser().getTokenLocation(),
            "It is forbidden to create dynamic nested objects ([" + dynamicObjectMapper.name() + "]) through `copy_to`"
        );
    }
    private static void parseArray(DocumentParserContext context, String lastFieldName) throws IOException {
        Mapper mapper = getLeafMapper(context, lastFieldName);
        if (mapper != null) {