Function make_audio_name 

fn make_audio_name(
    started_at: DateTime<Utc>,
    reflector: &str,
    module: &str,
    callsign: &str,
) -> String

Builds the audio part’s filename.

Format: YYYYMMDD_HHMMSS_<reflector>_<module>_<callsign>.mp3, derived from the stream’s started_at timestamp (UTC). Example:

20260412_143000_REF030_C_W1AW.mp3

The callsign is trimmed of trailing whitespace (D-STAR pads callsigns to 8 bytes on the wire) so the filename is not littered with padding.