Change move handler to carry blocks over (#14144)

* Change move handler to carry blocks and mutes over

When user A blocks user B and B moves to a new account C, make A block C
accordingly.

Note that it only works if A's instance is aware of the Move, that is,
if B is on A's instance or has followers there.

* Also notify instances with known people blocking you when moving

* Add automatic account notes when blocking/muting an account that had no note

spec/workers/activitypub/move_distribution_worker_spec.rb

@@ -0,0 +1,22 @@
+require 'rails_helper'
+
+describe ActivityPub::MoveDistributionWorker do
+  subject { described_class.new }
+
+  let(:migration)   { Fabricate(:account_migration) }
+  let(:follower) { Fabricate(:account, protocol: :activitypub, inbox_url: 'http://example.com') }
+  let(:blocker) { Fabricate(:account, protocol: :activitypub, inbox_url: 'http://example2.com') }
+
+  describe '#perform' do
+    before do
+      allow(ActivityPub::DeliveryWorker).to receive(:push_bulk)
+      follower.follow!(migration.account)
+      blocker.block!(migration.account)
+    end
+
+    it 'delivers to followers and known blockers' do
+      subject.perform(migration.id)
+        expect(ActivityPub::DeliveryWorker).to have_received(:push_bulk).with(['http://example.com', 'http://example2.com'])
+    end
+  end
+end