Federated reports (#6570)

* Fix #2176: Federated reports

* UI for federated reports

* Add spec for ActivityPub Flag handler

* Add spec for ReportService

app/lib/activitypub/activity.rb

@@ -44,6 +44,8 @@ class ActivityPub::Activity
         ActivityPub::Activity::Accept
       when 'Reject'
         ActivityPub::Activity::Reject
+      when 'Flag'
+        ActivityPub::Activity::Flag
       end
     end
   end

app/lib/activitypub/activity/flag.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class ActivityPub::Activity::Flag < ActivityPub::Activity
+  def perform
+    target_accounts            = object_uris.map { |uri| account_from_uri(uri) }.compact.select(&:local?)
+    target_statuses_by_account = object_uris.map { |uri| status_from_uri(uri) }.compact.select(&:local?).group_by(&:account_id)
+
+    target_accounts.each do |target_account|
+      next if Report.where(account: @account, target_account: target_account).exists?
+
+      target_statuses = target_statuses_by_account[target_account.id]
+
+      ReportService.new.call(
+        @account,
+        target_account,
+        status_ids: target_statuses.nil? ? [] : target_statuses.map(&:id),
+        comment: @json['content'] || ''
+      )
+    end
+  end
+
+  def object_uris
+    @object_uris ||= Array(@object.is_a?(Array) ? @object.map { |item| value_or_id(item) } : value_or_id(@object))
+  end
+end