Function encode_sum 

fn encode_sum(
    table_writer: &mut MultiTableData,
    name: &str,
    sum: &Sum,
    resource_attrs: Option<&Vec<KeyValue>>,
    scope_attrs: Option<&Vec<KeyValue>>,
    metric_ctx: &OtlpMetricCtx,
) -> Result<()>

Encodes sums, preserving delta points as interval values with a temporality tag. Ingestion is stateless: values are never accumulated across timestamps.