sources: fix sources sometimes choosing wrong strategy (fix #3968)

Fix sources choosing the wrong strategy when the referer belongs to a
different site (for example, when uploading a twitter post with a pixiv
referer).

* Fix `match?` to only consider the main url, not the referer.

* Change `match?` to match against a list of domains given by the `domains` method.

* Change `match?` to an instance method.

app/logical/sources/strategies/moebooru.rb

@@ -38,8 +38,8 @@ module Sources
 
       delegate :artist_name, :profile_url, :unique_id, :artist_commentary_title, :artist_commentary_desc, :dtext_artist_commentary_title, :dtext_artist_commentary_desc, to: :sub_strategy, allow_nil: true
 
-      def self.match?(*urls)
-        urls.compact.any? { |x| x.match?(BASE_URL) }
+      def domains
+        ["yande.re", "konachan.com"]
       end
 
       def site_name