### 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/DynamicFieldsBuilder.java
DateFormatter dateFormatter,
        CheckedRunnable<IOException> createDynamicField
    ) throws IOException {
        createDynamicField(context, name, DynamicTemplate.XContentFieldType.DATE, dateFormatter, createDynamicField);
    }
    private static void createDynamicField(
        DocumentParserContext context,
        String name,
        DynamicTemplate.XContentFieldType matchType,
        CheckedRunnable<IOException> dynamicFieldStrategy
    ) throws IOException {
        assert matchType != DynamicTemplate.XContentFieldType.DATE;
        createDynamicField(context, name, matchType, null, dynamicFieldStrategy);
    }
    private static void createDynamicField(
        DocumentParserContext context,
        String name,
        DynamicTemplate.XContentFieldType matchType,
        DateFormatter dateFormatter,
        CheckedRunnable<IOException> dynamicFieldStrategy
    ) throws IOException {
        if (applyMatchingTemplate(context, name, matchType, dateFormatter) == false) {
            dynamicFieldStrategy.run();
        }
    }
    /**
     * Find and apply a matching dynamic template. Returns {@code true} if a template could be found, {@code false} otherwise.
     * @param context        the parse context for this document
     * @param name           the current field name
     * @param matchType      the type of the field in the json document or null if unknown