Allow attendance_id to be changed during session #17
Description
Currently the attendance_id file is rescanned and its contents retried until the server returns a 200 OK for that ID. From that point on, it doesn't rescan the file and will quit if the attendance_id is invalidated by the server.
But the server never invalidates old IDs and learners often launch with old IDs, so it would be an improvement to re-read the attendance_id under any circumstances.
It would make sense for it to replicate the current behaviour and only "stick" on an attendance_id value that has received a 200 response from the server.