ActivityPub delivery (#4566)

* Deliver ActivityPub Like

* Deliver ActivityPub Undo-Like

* Deliver ActivityPub Create/Announce activities

* Deliver ActivityPub creates from mentions

* Deliver ActivityPub Block/Undo-Block

* Deliver ActivityPub Accept/Reject-Follow

* Deliver ActivityPub Undo-Follow

* Deliver ActivityPub Follow

* Deliver ActivityPub Delete activities

Incidentally fix #889

* Adjust BatchedRemoveStatusService for ActivityPub

* Add tests for ActivityPub workers

* Add tests for FollowService

* Add tests for FavouriteService, UnfollowService and PostStatusService

* Add tests for ReblogService, BlockService, UnblockService, ProcessMentionsService

* Add tests for AuthorizeFollowService, RejectFollowService, RemoveStatusService

* Add tests for BatchedRemoveStatusService

* Deliver updates to a local account to ActivityPub followers

* Minor adjustments

spec/workers/activitypub/delivery_worker_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ActivityPub::DeliveryWorker do
+  subject { described_class.new }
+
+  let(:sender)  { Fabricate(:account) }
+  let(:payload) { 'test' }
+
+  describe 'perform' do
+    it 'performs a request' do
+      stub_request(:post, 'https://example.com/api').to_return(status: 200)
+      subject.perform(payload, sender.id, 'https://example.com/api')
+      expect(a_request(:post, 'https://example.com/api')).to have_been_made.once
+    end
+
+    it 'raises when request fails' do
+      stub_request(:post, 'https://example.com/api').to_return(status: 500)
+      expect { subject.perform(payload, sender.id, 'https://example.com/api') }.to raise_error Mastodon::UnexpectedResponseError
+    end
+  end
+end