Implement Undo { Accept { Follow } } (fixes #8234) (#8245)

* Add Follow#revoke_request!

* Implement Undo { Accept { Follow } } (fixes #8234)

app/lib/activitypub/activity/undo.rb

@@ -5,6 +5,8 @@ class ActivityPub::Activity::Undo < ActivityPub::Activity
     case @object['type']
     when 'Announce'
       undo_announce
+    when 'Accept'
+      undo_accept
     when 'Follow'
       undo_follow
     when 'Like'
@@ -27,6 +29,10 @@ class ActivityPub::Activity::Undo < ActivityPub::Activity
     end
   end
 
+  def undo_accept
+    ::Follow.find_by(target_account: @account, uri: target_uri)&.revoke_request!
+  end
+
   def undo_follow
     target_account = account_from_uri(target_uri)
 

app/models/follow.rb

@@ -32,6 +32,11 @@ class Follow < ApplicationRecord
     false # Force uri_for to use uri attribute
   end
 
+  def revoke_request!
+    FollowRequest.create!(account: account, target_account: target_account, show_reblogs: show_reblogs, uri: uri)
+    destroy!
+  end
+
   before_validation :set_uri, only: :create
   after_destroy :remove_endorsements