* Allow Card#last_updated_at to be set
This is useful when doing an import from another system. I'm currently
working on a script to import our Github issues into Fizzy.
This is discussed in
https://github.com/basecamp/fizzy/pull/2056#discussion_r2609560246
* Add nil fallback and expand test coverage for last_active_at
Adds a safety fallback to Time.current if created_at is unexpectedly nil
during card creation.
Test coverage to verify:
* last_active_at defaults to created_at when not provided
* last_active_at can be updated via API on existing cards
* import workflow where last_active_at is restored after comments
* publishing doesn't overwrite explicit last_active_at values
---------
Co-authored-by: Jeremy Daer <jeremy@37signals.com>
Jankees van Woezik