Add ActivityPub Actor id to WebFinger JSON. (#2522)

app/views/well_known/webfinger/show.json.rabl

@@ -10,6 +10,7 @@ node(:links) do
   [
     { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: TagManager.instance.url_for(@account) },
     { rel: 'http://schemas.google.com/g/2010#updates-from', type: 'application/atom+xml', href: account_url(@account, format: 'atom') },
+    { rel: 'self', type: 'application/activity+json', href: TagManager.instance.url_for(@account) },
     { rel: 'salmon', href: api_salmon_url(@account.id) },
     { rel: 'magic-public-key', href: "data:application/magic-public-key,#{@magic_key}" },
     { rel: 'http://ostatus.org/schema/1.0/subscribe', template: "#{authorize_follow_url}?acct={uri}" },