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/hentai_foundry.rb

@@ -62,4 +62,8 @@ class Source::URL::HentaiFoundry < Source::URL
     else
     end
   end
+
+  def profile_url
+    "https://www.hentai-foundry.com/user/#{username}" if username.present?
+  end
 end