Function upsert 

pub(crate) async fn upsert(
    pool: &PgPool,
    callsign: &str,
    protocol: &str,
    ip_address: Option<&str>,
    dashboard_url: Option<&str>,
    country: Option<&str>,
) -> Result<(), Error>

Inserts a new reflector or updates an existing one on callsign conflict.

Executes an INSERT ... ON CONFLICT (callsign) DO UPDATE so that repeated discovery sweeps refresh metadata without requiring a separate existence check.

Errors

Returns sqlx::Error on connection or constraint failures.