Worker: do something better when the JWT expires

We've had some problems lately with the JWT on the run channel expiring , causing messages to fail.

It looks a bit like this:

The worker should do better in these cases, throwing a clear error and existing the channel and maybe the socket.

The question is WHERE we report. We can't tell lightning because, well, the JWT expired. Any attempts to send a message back will be rejected.

This comes into monitoring - we don't have a monitoring solution yet, other than lightning and GCP.

Perhaps a good approach is to shut the whole server down (probably gracefully) with a clear error like "expired JWT detected" and stop requesting traffic. That depends a bit whether it's one run that's expired or whether all JWTs are wrong.

We probably don't unit test for any of this very well at the moment. I think unit testing and clear logs to GCP are the first step. That also makes it easier for us to trace where to add more monitoring later.

Start by locating the worker's run-channel JWT handling and any existing unit tests or GCP logging for expiry failures. Define the behavior for one expired run versus invalid JWTs generally, then add tests and clear logging that verify the chosen graceful channel, socket, or server shutdown behavior.