Fix serialization of quote policies in nested quotes (#35828)

app/serializers/rest/shallow_status_serializer.rb

@@ -6,4 +6,5 @@ class REST::ShallowStatusSerializer < REST::StatusSerializer
   # It looks like redefining one `has_one` requires redefining all inherited ones
   has_one :preview_card, key: :card, serializer: REST::PreviewCardSerializer
   has_one :preloadable_poll, key: :poll, serializer: REST::PollSerializer
+  has_one :quote_approval, if: -> { Mastodon::Feature.outgoing_quotes_enabled? }
 end

app/serializers/rest/status_serializer.rb

@@ -29,6 +29,8 @@ class REST::StatusSerializer < ActiveModel::Serializer
   has_many :tags
   has_many :emojis, serializer: REST::CustomEmojiSerializer
 
+  # Due to a ActiveModel::Serializer quirk, if you change any of the following, have a look at
+  # updating `app/serializers/rest/shallow_status_serializer.rb` as well
   has_one :quote, key: :quote, serializer: REST::QuoteSerializer
   has_one :preview_card, key: :card, serializer: REST::PreviewCardSerializer
   has_one :preloadable_poll, key: :poll, serializer: REST::PollSerializer