Function round_trip 

pub async fn round_trip(
    endpoint: &Endpoint,
    topic: &str,
    partition: i32,
) -> Result<i64, String>

Produce one record to topic-partition with acks=all, then read it back at the offset it was acknowledged at, and return that offset.

This is what “serving” means after a restore: a client of the restored cluster, authenticated as an ordinary principal, can write and then read.

Errors

Returns why the write or the read failed, or that the record did not come back within a minute.