influx: Backup to file

[BlakeFreer]

From lib/rust/influx/src/lib.rs

tracing::debug!("Making Influx request");
let response = request.send().await;

match response {
    Ok(r) => tracing::debug!(response=?r, "Received Influx response"),
    Err(e) => tracing::error!(err = ?e, "Failed to write to DB"),
}

batch.clear();

If response is Err (database request fails), the queries are dropped. Instead, they should be saved to a local file and pushed once the connection is live

There is an unused backup_file on the Logger object already. Use it.