BREAKING CHANGES:
The flag --es.slm has been renamed to --collector.slm.
The logging system has been replaced with log/slog from the stdlib. This change is being made across the prometheus ecosystem. The logging output has changed, but the messages and levels remain the same. The ts label for the timestamp has bewen replaced with time, the accuracy is less, and the timezone is not forced to UTC. The caller field has been replaced by the source field, which now includes the full path to the source file. The level field now exposes the log level in capital letters.