Function deltachat::imex::get_next_backup_path

fn get_next_backup_path(
    folder: &Path,
    addr: &str,
    backup_time: i64
) -> Result<(PathBuf, PathBuf, PathBuf)>

Returns Ok((temp_db_path, temp_path, dest_path)) on success. Unencrypted database can be written to temp_db_path. The backup can then be written to temp_path. If the backup succeeded, it can be renamed to dest_path. This guarantees that the backup is complete.