Why this change?
Back in May 17 2023 along with the release of Discourse 3.1, we announced
on meta that the legacy hamburger dropdown navigation menu is
deprecated and will be dropped in Discourse 3.2. This is the link to the announcement
on meta: https://meta.discourse.org/t/removing-the-legacy-hamburger-navigation-menu-option/265274
## What does this change do?
This change removes the `legacy` option from the `navigation_menu` site
setting and migrates existing sites on the `legacy` option to the
`header dropdown` option.
All references to the `legacy` option in code and tests have been
removed as well.
This new site setting replaces the
`enable_experimental_sidebar_hamburger` and `enable_sidebar` site
settings as the sidebar feature exits the experimental phase.
Note that we're replacing this without depreciation since the previous
site setting was considered experimental.
Internal Ref: /t/86563
Users who can access the review queue can claim a pending reviewable(s) which means that the claimed reviewable(s) can only be handled by the user who claimed it. Currently, we show claimed reviewables in the user menu, but this can be annoying for other reviewers because they can't do anything about a reviewable claimed by someone. So this PR makes sure that we only show in the user menu reviewables that are claimed by nobody or claimed by the current user.
Internal topic: t/77235.
I'm hesitant to call this a performance improvement since claiming a
reviewable is probably rare. However, this commit cuts out two DB
queries each time we have to publish a reviewable claimed message. More
importantly, publishing to groups scales much better than publishing to
users because we esstentially cap the number ids we have to load into
memory.
This is a feature that used to be present in discourse-assign but is
much easier to implement in core. It also allows a topic to be assigned
without it claiming for review and vice versa and allows it to work with
category group reviewers.
