Changes:
* Drop Users.id_to_name.
* Don't cache Users.name_to_id.
* Replace calls to name_to_id with find_by_name when possible.
* Don't autodefine creator_name in belongs_to_creator.
* Don't autodefine updater_name in belongs_to_updater.
* Instead manually define creator_name / updater_name only on models that need
to return these fields in the api.
id_to_name was cached to reduce the impact of N+1 query patterns in
certain places, especially in api responses that return creator_name /
updater_name fields. But it still meant we were doing N calls to
memcache. Using `includes` to prefetch users avoids this N+1 pattern.
name_to_id had no need be cached, it was never used in any performance-
sensitive contexts.
Avoiding caching also avoids the need to keep these caches consistent.
Avoid some queries used in wiki page excerpts:
* Only try to load the artist if the tag is an artist tag.
* Avoid using `exists?` queries for wiki pages.
* Bugfix: don't show wiki excerpts for deleted wikis.
https://danbooru.donmai.us/forum_topics/9127?page=265#forum_post_153180:
> I'm not sure how to reproduce this, but sometimes on the upload page
> when I click the button to pop out the tag box, the screen scrolls up to
> the picture but the box doesn't pop out, and I have to scroll back down
> and click it again
https://danbooru.donmai.us/forum_topics/9127?page=266#forum_post_153183:
> Yes, this was brought up by Unbreakable on Discord a while back. It's
> due to the fact that the event handler that pops out the dialog box has
> not yet been bound by the time you click it. Since that clickable
> control has an empty anchor link of "#" which goes nowhere, it therefore
> redirects the user to the top of the page.
Fix exception in Pool#previous_post_id when the post id is not contained
in the pool.
This can happen when a post's pool_string lists the post as being in a
certain pool, but the post is not included in the pool's post_ids. Such
pool_string / post_ids inconsistencies exist because of past bugs.
Refactor the /related_tags.js call so that when the "Related tags"
button is clicked, it only replaces the columns that actually changed,
not the entire related tags section.
This avoids rebuilding the Recent / Frequent / Translated Tags / Artist
columns every time the "Related tags" button is clicked.
Move PostPresenter#categorized_tag_groups to TagSetPresenter#split_tag_list_text.
This allows split_tag_list_text to reuse the same set of tags already
fetched by the tag set presenter for the sidebar.
This avoids a memcache call to get the tag categories when rendering the
tag string for the post edit form.
* Move the limit:<n> / order:random metatag parsing from the controller
to the post set.
* Introduce `Tag.has_metatag?` and use it to parse these metatags
instead of using a regex (#2894).
* On posts, automatically trigger "Fetch source data" when clicking the
Edit tab, instead of triggering the artist finder button. This way we
find both the artist and the translated tags in one ajax call.
* Remove the "Artist" finder button next to the source field. This isn't
necessary given that "Fetch source data" finds the artist itself.
* Remove the /artists/finder.json API endpoint. This is no longer used
after removing the "Artist" finder button.
* Consolidate blacklist css in one file.
* blacklist box: fix tag colors not dimming on hover.
* blacklist box: allow middle clicking on tags to open in new tab.
* /wiki_pages: move blacklist controls to top of tag sidebar.
* /wiki_pages: fix missing "disable all" / "re-enable all" buttons.
