Function reencrypt_private_config 

pub fn reencrypt_private_config(
    data_dir: &Path,
    private_config: &ServerConfigPrivate,
    new_password: &str,
) -> Result<()>

Re-encrypts the private config with a new password.

Note that we assume that the in-memory secret config equals the on-disk secret config. If the process is interrupted, recover_interrupted_password_change will fix it on startup.

As an additional safetynet this function creates backup copies of all files being overwritten. These will be deleted by finalize_password_change after the config has been read successfully for the first time after a password change.