sources: add artist profile links to fetch source data box.

Add site icons linking to all the artist's sites in the fetch source
data box.

Some artist entries have a large number of URLs. Various heuristics are
applied to try to present the most useful URLs first. Dead URLs and
redundant URLs (Pixiv stacc and Twitter intent URLs) are filtered out.
Remaining URLs are sorted first by site (to put sites like Pixiv and
Twitter first), then by URL (to break ties when an artist has multiple
accounts on the same site).

Some sites have shitty hard-to-read icons. It can't be helped. The icons
are the official favicons of each site.

app/models/artist_url.rb

@@ -7,6 +7,7 @@ class ArtistUrl < ApplicationRecord
 
   scope :url_matches, ->(url) { url_attribute_matches(:url, url) }
   scope :normalized_url_matches, ->(url) { url_attribute_matches(:normalized_url, url) }
+  scope :active, -> { where(is_active: true) }
 
   def self.parse_prefix(url)
     prefix, url = url.match(/\A(-)?(.*)/)[1, 2]
@@ -68,24 +69,51 @@ class ArtistUrl < ApplicationRecord
     end
   end
 
-  def priority
-    if normalized_url =~ /pixiv\.net\/member\.php/
-      10
+  def domain
+    uri = Addressable::URI.parse(normalized_url)
+    uri.domain
+  end
 
-    elsif normalized_url =~ /seiga\.nicovideo\.jp\/user\/illust/
-      10
-
-    elsif normalized_url =~ /twitter\.com/ && normalized_url !~ /status/
-      15
-
-    elsif normalized_url =~ /tumblr|patreon|deviantart|artstation/
-      20
+  def site_name
+    source = Sources::Strategies.find(normalized_url)
+    source.site_name
+  end
 
+  # A secondary URL is an artist URL that we don't normally want to display,
+  # usually because it's redundant with the primary profile URL.
+  def secondary_url?
+    case url
+    when %r!pixiv\.net/stacc!i
+      true
+    when %r!pixiv\.net/fanbox!i
+      true
+    when %r!twitter\.com/intent!i
+      true
+    when %r!lohas\.nicoseiga\.jp!i
+      true
+    when %r!(?:www|com|dic)\.nicovideo\.jp!i
+      true
+    when %r!pawoo\.net/web/accounts!i
+      true
+    when %r!www\.artstation\.com!i
+      true
     else
-      100
+      false
     end
   end
 
+  # The sort order of sites in artist URL lists.
+  def priority
+    sites = %w[
+      Pixiv Twitter
+      ArtStation Deviant\ Art Nico\ Seiga Nijie pawoo.net Pixiv\ Fanbox Pixiv\ Sketch Tinami Tumblr
+      Booth.pm Facebook Fantia FC2 Gumroad Instagram Lofter Patreon Privatter Skeb Weibo Youtube
+      Circle.ms DLSite Melonbooks Toranoana
+    ]
+
+    sites.index(site_name) || 1000
+  end
+
   def normalize
     # Perform some normalization with Addressable on the URL itself
     # - Converts scheme and hostname to downcase