The twitter gem had several problems:
* It's been unmaintained for over a year.
* It pulled in a lot of dependencies, many of which were outdated. In
particular, it locked the `http` gem to version 3.3, preventing us
from upgrading to 4.2.
* It raised exceptions on normal error conditions, like for deleted
tweets or suspended users, which we really don't want.
* We had to wrap it to provide caching.
Changes:
* Fixes#4226 (Exception when creating new artists entries for suspended
Twitter accounts)
* Drop support for scraping images from summary cards. Summary cards
are the previews you get when you link to a website in a tweet. These
preview images aren't always the best image.
* B2 doesn't allow the path to start with a '/' character.
* When storing the file, we have to rewind the file pointer to make sure
we get the whole file.
Fix an error in operator precedence:
> sum + Tag.find_by_name(token[1]).try(:post_count) || 0
This was treated as `(sum + X) || 0` not `sum + (X || 0)` as intended.
This failed when X was nil.
* Fix the post-upgrade message showing the gift message instead of the
normal upgrade message.
* Link back to Danbooru so people don't stay on Safebooru and get
confused when they can't see hidden posts.
* Add favorite count beneath recommended posts. Clicking the favcount
loads more recommended posts like that post.
* Increase number of recommendations shown on post show page.
Filter out the user's own uploads and favorites from their
recommendations.
Note that in most cases a user's top-N recommendations will be things
they've already favorited. If a user has 10,000 favorites, most of their
top 10,000 recommendations will be their own favorites, so we have to
generate a little more than 10,000 recommendations to be sure they won't
all be filtered out.
In other words, the more favorites a user has, the more recommendations
we have to generate. The upper bound is clamped to 50,000 for
performance reasons. If a user has more favorites than this we may not
be able to find any recommendations for them.
* Open recommendations to all users (not just gold).
* Show recommendations on all posts (not just posts after 2017).
* Allow users to browse recommendations for other users.
* Increase number of recommended posts returned.
* Change endpoints to /recommended_posts?user_id=1234 and
/recommended_posts?post_id=1234 and add json/xml support.
