* Refactor the paginator into a ViewComponent.
* Fix inconsistent spacing between paginator items.
* Fix a bug where the sequential paginator generated the wrong next /
previous page links in the <link rel="{next|prev}"> tags in the <head>.
* Always include the final page as a hidden html element, so that it can
be unhidden with custom CSS.
* Make it easier to change the pagination window.
Refactor page limits to a) be explicitly listed in the User class (not
hidden away in the Danbooru config) and b) explicitly depend on the
CurrentUser (not implicitly by way of Danbooru.config.max_numbered_pages).
Rework sitemaps to provide more coverage of the site. We want every
important page on the site - including every post, tag, and wiki page -
to be indexed by Google. We do this by generating sitemaps and sitemap
indexes that contain links to every important page on the site.
Bug: when a search timed out we got the generic failbooru page instead
of the search timeout error page.
Cause: when rendering the <link rel="next"> / <link rel="prev"> tags in
the header, we may need to evaluate the search to determine the next or
previous page, but if the searches times out then this fails, which
caused Rails to throw a ActionView::Template::Error because an exception
was thrown while rendering the template.
Likewise, rendering the attributes for the <body> tag could fail with an
ActionView::Template::Error because the call to `current_item.present?`
forced evaluation of the search.
Bug: if there was a timeout when calculating the page count, the timeout
wouldn't be cached, so we would hit multiple timeouts trying to
calculate the page count multiple times.
Fix an invalid SQL exception that occurs when the paginator tries to
do a COUNT(*) to calculate the page count of a relation that already
includes a GROUP BY + COUNT(*) clause. We need to nest the whole query
inside a `SELECT COUNT(*) FROM (...)` subquery so the inner COUNT(*)
doesn't mess up the outer COUNT(*).
Fixes#4285.
Add <link rel="prev"> and <link rel="next"> elements to most pages with
pagination. This should work on all index pages, but it won't work for
things like pool or forum topic show pages.
Also remove the <link rel="top"> element (wasn't useful, was just a link
back to the root url).
Previously the page-based (numbered) paginator would always count the
total_pages, even in API calls when it wasn't needed. This could be very
slow in some cases. Refactor so that total_pages isn't calculated unless
it's called.
While we're at it, refactor to condense all the sequential vs. numbered
pagination logic into one module. This incidentally fixes a couple more
bugs:
* "page=b0" returned all pages rather than nothing.
* Bad parameters like "page=blaha123" and "page=a123blah" were accepted.
