Add ActivityPub actor representing the entire server (#11321)

* Add support for an instance actor

* Skip username validation for local Application accounts

* Add migration script to create instance actor

* Make Codeclimate happy

* Switch to id -99 for instance actor

* Remove unused `icon` and `image` attributes from instance actor

* Use if/elsif/else instead of return + ternary operator

* Add instance actor to fresh installs

* Use instance actor as instance representative

Use instance actor for forwarding reports, relay operations, and spam
auto-reporting.

* Seed database in test environment

* Fix single-user mode

* Fix tests

* Fix specs to accomodate for an extra `Account`

* Auto-reject follows on instance actor

Following an instance actor might make sense, but we are not handling that
right now, so auto-reject.

* Fix webfinger lookup and serialization for instance actor

* Rename instance actor

* Make it clear in the HTML view that the instance actor should not be blocked

* Raise cache time for instance actor as there's no dynamic content

* Re-use /about/more with a flash message for instance actor profile

1 files changed, 10 insertions, 4 deletions

diff --git a/app/serializers/activitypub/actor_serializer.rb b/app/serializers/activitypub/actor_serializer.rb
index 0644219fb..0bd7aed2e 100644
--- a/app/serializers/activitypub/actor_serializer.rb
+++ b/app/serializers/activitypub/actor_serializer.rb
@@ -39,11 +39,17 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
   delegate :moved?, to: :object
 
   def id
-    account_url(object)
+    object.instance_actor? ? instance_actor_url : account_url(object)
   end
 
   def type
-    object.bot? ? 'Service' : 'Person'
+    if object.instance_actor?
+      'Application'
+    elsif object.bot?
+      'Service'
+    else
+      'Person'
+    end
   end
 
   def following
@@ -55,7 +61,7 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
   end
 
   def inbox
-    account_inbox_url(object)
+    object.instance_actor? ? instance_actor_inbox_url : account_inbox_url(object)
   end
 
   def outbox
@@ -95,7 +101,7 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
   end
 
   def url
-    short_account_url(object)
+    object.instance_actor? ? about_more_url(instance_actor: true) : short_account_url(object)
   end
 
   def avatar_exists?