Fix a potential exploit where private information could be leaked if
it was contained in the error message of an unexpected exception.
For example, NoMethodError contains a raw dump of the object in the
error message, which could leak private user data if you could force a
User object to raise a NoMethodError.
Fix the error page to only show known-safe error messages from expected
exceptions, not unknown error messages from unexpected exceptions.
API changes:
* JSON errors now have a `message` param. The message will be blank for unknown exceptions.
* XML errors have a new format. This is a breaking change. They now look like this:
<result>
<success type="boolean">false</success>
<error>PaginationExtension::PaginationError</error>
<message>You cannot go beyond page 5000.</message>
<backtrace type="array">
<backtrace>app/logical/pagination_extension.rb:54:in `paginate'</backtrace>
<backtrace>app/models/application_record.rb:17:in `paginate'</backtrace>
<backtrace>app/logical/post_query_builder.rb:529:in `paginated_posts'</backtrace>
<backtrace>app/logical/post_sets/post.rb:95:in `posts'</backtrace>
<backtrace>app/controllers/posts_controller.rb:22:in `index'</backtrace>
</backtrace>
</result>
instead of like this:
<result success="false">You cannot go beyond page 5000.</result>
Standardize font sizes and heading tags (<h1>-<h6>) to be more
consistent across the site.
Changes:
* Introduce font size CSS variables and start replacing hardcoded font
sizes with standard sizes.
* Change header tags to use only one <h1> per page. One <h1> per page is
recommended for SEO purposes. Usually this is for the page title, like
in forum threads or wiki pages.
* Standardize on <h2> for section headers in sidebars and <h3> for
smaller subsection headers. Don't use <h4>-<h6>.
* In DText, make h1-h4 headers all the same size. Standard wiki style is
to ignore h1-h3 and start at h4.
* In DText, make h4-h6 the same size as the h1-h3 tags outside of DText.
* In the tag list, change the <h1> and <h2> tag category headers to <h3>.
* Make usernames in comments and forum posts smaller. Also change the
<h4> tag for the commenter name to <div class="author-name">.
* Make the tag list, paginator, and nav menu smaller on mobile.
* Change h1#app-name-header to a#app-name-header.
* Simplify code.
* Show backtraces for all users, not just builders.
* Show backtraces only for unexpected server errors (status 5xx), not
for normal client errors (status 4xx).
* Log expected errors at info level (reduce noise in production logs).
Fixes an "incompatible character encodings: UTF-8 and ASCII-8BIT"
exception when uploading a deleted Pixiv post.
Caused by the Pixiv API error message not having the encoding set to UTF-8.
