Function decode

fn decode(
    decoder: &SqlServerRowDecoder,
    row: &Row,
    mz_row: &mut Row,
    arena: &RowArena,
    new_row: Option<&Row>,
) -> Result<SourceMessage, DataflowError>

Helper method to decode a row from a tiberius::Row (or 2 of them in the case of update) to a Row. This centralizes the decode and mapping to result.