test(transcription): cover speaker and track resolution
These tests show the order of the three sources for the track sid, and the choice of the speaker.
- The attribute wins when it is present.
- Without the attribute, the microphone track of the speaker is used.
- For an avatar session, the converter names the worker that publishes for the agent. It also uses
the microphone track of that worker.
- If the worker has no microphone track, the converter uses the track of the sender.
- If nothing is found, the track sid stays empty.
- A callback that returns an empty string means "nothing found". The converter goes on to the next
source. It does not stop.
