Source::URL: add profile_url method.

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.

app/logical/source/url/fantia.rb

@@ -76,6 +76,10 @@ class Source::URL::Fantia < Source::URL
     end
   end
 
+  def profile_url
+    "https://fantia.jp/fanclubs/#{fanclub_id}" if fanclub_id.present?
+  end
+
   def work_id
     @post_id || @product_id
   end