### 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/vectors/DenseVectorFieldMapper.java
}
            @Override
            IndexFieldData.Builder fielddataBuilder(DenseVectorFieldType denseVectorFieldType, FieldDataContext fieldDataContext) {
                return new VectorIndexFieldData.Builder(
                    denseVectorFieldType.name(),
                    CoreValuesSourceType.KEYWORD,
                    denseVectorFieldType.indexVersionCreated,
                    this,
                    denseVectorFieldType.dims,
                    denseVectorFieldType.indexed
                );
            }
            @Override
            public void checkVectorBounds(float[] vector) {
                checkNanAndInfinite(vector);
            }
            @Override
            void checkVectorMagnitude(
                IndexVersion indexVersion,
                VectorSimilarity similarity,
                Function<StringBuilder, StringBuilder> appender,
                float squaredMagnitude
            ) {
                StringBuilder errorBuilder = null;
                if (indexVersion.before(DOT_PRODUCT_AUTO_NORMALIZED)) {
                    if (similarity == VectorSimilarity.DOT_PRODUCT && Math.abs(squaredMagnitude - 1.0f) > EPS) {
                        errorBuilder = new StringBuilder(
                            "The [" + VectorSimilarity.DOT_PRODUCT + "] similarity can only be used with unit-length vectors."
                        );
                    }