Federated reports (#6570)

* Fix #2176: Federated reports

* UI for federated reports

* Add spec for ActivityPub Flag handler

* Add spec for ReportService

spec/lib/activitypub/activity/flag_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Flag do
+  let(:sender)  { Fabricate(:account, domain: 'example.com') }
+  let(:flagged) { Fabricate(:account) }
+  let(:status)  { Fabricate(:status, account: flagged, uri: 'foobar') }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: nil,
+      type: 'Flag',
+      content: 'Boo!!',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: [
+        ActivityPub::TagManager.instance.uri_for(flagged),
+        ActivityPub::TagManager.instance.uri_for(status),
+      ],
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'creates a report' do
+      report = Report.find_by(account: sender, target_account: flagged)
+
+      expect(report).to_not be_nil
+      expect(report.comment).to eq 'Boo!!'
+      expect(report.status_ids).to eq [status.id]
+    end
+  end
+end