Add a method for converting a source URL into a profile URL. This will
be used for normalizing profile URLs in artist entries.
Also add the ability to parse a few more profile URL formats.
Remove the `preview_urls` method from strategies. The only place this was used was
when doing IQDB searches, to download the thumbnail image from the source instead of
the full image.
This wasn't worth it for a few reasons:
* Thumbnails on other sites are sometimes not the size we want, which could affect
IQDB results.
* Grabbing thumbnails is complex for some sites. You can't always just rewrite the
image URL. Sometimes it requires extra API calls, which can be slower than just
grabbing the full image.
* For videos and animations, thumbnails from other sites don't always match our
thumbnails. We do smart thumbnail generation to try to avoid blank thumbnails, which
means we don't always pick the first frame, which could affect IQDB results.
API changes:
* /iqdb_queries?search[file_url] now downloads the URL as is without any modification.
Before it tried to change thumbnail and sample size image URLs to the full version.
* /iqdb_queries?search[url] now returns an error if the URL is for a HTML page that
contains multiple images. Before it would grab only the first image and silently
ignore the rest.
Additionally, fixed some broken tests and changed normalization for urls
of album type to point to the mobile version instead, because they're
only visible to logged-in users.
Get rid of `normalized_for_artist_finder?` and `normalizable_for_artist_finder?`.
This was legacy bullshit that was originally designed to avoid API calls
when saving artist entries containing old Pixiv direct image urls that
had already been normalized, or that couldn't be normalized because they
were bad id.
Nowadays we store profile urls in artist entries instead of direct image
urls, so we don't normally need to do any API calls to normalize the
profile url. Strategies should take care to avoid triggering API calls
inside `profile_url` when possible.
