Fixescoder/internal#281

There was a TOCTOU race between checking whether the notifier should pause and processing the messages:

// run is the main loop of the notifier.func (n*notifier)run(ctx context.Context,successchan<-dispatchResult,failurechan<-dispatchResult)error {...for {...// Check if notifier is not paused.ok,err:=n.ensureRunning(ctx)iferr!=nil {n.log.Warn(ctx,"failed to check notifier state",slog.Error(err))    }ifok {// <---- if the notifier was paused at this point, any pending messages would still be processed.// Call process() immediately (i.e. don't wait an initial tick).err=n.process(ctx,success,failure)iferr!=nil {n.log.Error(ctx,"failed to process messages",slog.Error(err))    }    }...  }...

I'm of the opinion that we don't need to fix this in the code itself (it's not super critical that pausing the notifier is effectedimmediately); it was just a problem for the tests.

Previously in the tests:

1. The manager was started first
2. A message was enqueued
3. Notifier ticked, to process notifications
4. Notifier is determined to be paused (while already inprocess method) <--TOCTOU
5. Notification is processed

Now:

1. Message is enqueued
2. Manager is started
3. Notifier ticked, to process notifications
4. Notifier is determined to be paused,process method exits