Improve ActivityPub representations (#3844)

* Improve webfinger templates and make tests more flexible

* Clean up AS2 representation of actor

* Refactor outbox

* Create activities representation

* Add representations of followers/following collections, do not redirect /users/:username route if format is empty

* Remove unused translations

* ActivityPub endpoint for single statuses, add ActivityPub::TagManager for better
URL/URI generation

* Add ActivityPub::TagManager#to

* Represent all attachments as Document instead of Image/Video specifically
(Because for remote ones we may not know for sure)

Add mentions and hashtags representation to AP notes

* Add AP-resolvable hashtag URIs

* Use ActiveModelSerializers for ActivityPub

* Clean up unused translations

* Separate route for object and activity

* Adjust cc/to matrices

* Add to/cc to activities, ensure announce activity embeds target status and
not the wrapper status, add "id" to all collections

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

@@ -3,14 +3,14 @@ object @account
 node(:subject) { @canonical_account_uri }
 
 node(:aliases) do
-  [TagManager.instance.url_for(@account), TagManager.instance.uri_for(@account)]
+  [short_account_url(@account), account_url(@account)]
 end
 
 node(:links) do
   [
-    { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: TagManager.instance.url_for(@account) },
+    { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: account_url(@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: 'self', type: 'application/activity+json', href: account_url(@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}" },