Function record 

pub fn record(
    conn: &Connection,
    s: &Stream<'_>,
    content: &str,
    masked: &str,
    exposed: &str,
    cause: &str,
    actor: Option<&str>,
) -> Result<Option<i64>, String>

Records a snapshot when content differs from the stream’s latest. Returns the new sequence number, or None when nothing changed (or history is off).