Change grouped notifications API shape (take 2) (#31214)

app/serializers/rest/dedup_notification_group_serializer.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class REST::DedupNotificationGroupSerializer < ActiveModel::Serializer
+  has_many :accounts, serializer: REST::AccountSerializer
+  has_many :statuses, serializer: REST::StatusSerializer
+  has_many :notification_groups, serializer: REST::NotificationGroupSerializer
+end

app/serializers/rest/notification_group_serializer.rb

@@ -8,12 +8,20 @@ class REST::NotificationGroupSerializer < ActiveModel::Serializer
   attribute :page_max_id, if: :paginated?
   attribute :latest_page_notification_at, if: :paginated?
 
-  has_many :sample_accounts, serializer: REST::AccountSerializer
-  belongs_to :target_status, key: :status, if: :status_type?, serializer: REST::StatusSerializer
+  attribute :sample_account_ids
+  attribute :status_id, if: :status_type?
   belongs_to :report, if: :report_type?, serializer: REST::ReportSerializer
   belongs_to :account_relationship_severance_event, key: :event, if: :relationship_severance_event?, serializer: REST::AccountRelationshipSeveranceEventSerializer
   belongs_to :account_warning, key: :moderation_warning, if: :moderation_warning_event?, serializer: REST::AccountWarningSerializer
 
+  def sample_account_ids
+    object.sample_accounts.pluck(:id).map(&:to_s)
+  end
+
+  def status_id
+    object.target_status&.id&.to_s
+  end
+
   def status_type?
     [:favourite, :reblog, :status, :mention, :poll, :update].include?(object.type)
   end