* [x] Log updates to last message (message preview) in conversation list.
Should help debug cases such as:
https://github.com/signalapp/Signal-Desktop/issues/2323
* [x] Use structured logs:
* [x] Use static prefix (easier to search)
* [x] Capitalize log message and use present tense
(consistent with Git logging conventions).
* [x] Attach metadata as JSON serializable object. This has the benefit
that all fields are named and can be searched for.
* [x] Remove newlines from group IDs during redaction so they don’t break up
log lines.