Accept remote quotes of local quotes according to set policy (#35629)

app/lib/activitypub/activity/quote_request.rb

@@ -9,12 +9,31 @@ class ActivityPub::Activity::QuoteRequest < ActivityPub::Activity
     quoted_status = status_from_uri(object_uri)
     return if quoted_status.nil? || !quoted_status.account.local? || !quoted_status.distributable?
 
-    # For now, we don't support being quoted by external servers
-    reject_quote_request!(quoted_status)
+    if Mastodon::Feature.outgoing_quotes_enabled? && StatusPolicy.new(@account, quoted_status).quote?
+      accept_quote_request!(quoted_status)
+    else
+      reject_quote_request!(quoted_status)
+    end
   end
 
   private
 
+  def accept_quote_request!(quoted_status)
+    status = status_from_uri(@json['instrument'])
+    # TODO: import inlined quote post if possible
+    status ||= ActivityPub::FetchRemoteStatusService.new.call(@json['instrument'], on_behalf_of: @account.followers.local.first, request_id: @options[:request_id])
+    # TODO: raise if status is nil
+
+    # Sanity check
+    return unless status.quote.quoted_status == quoted_status
+
+    status.quote.update!(activity_uri: @json['id'])
+    status.quote.accept!
+
+    json = Oj.dump(serialize_payload(status.quote, ActivityPub::AcceptQuoteRequestSerializer))
+    ActivityPub::DeliveryWorker.perform_async(json, quoted_status.account_id, @account.inbox_url)
+  end
+
   def reject_quote_request!(quoted_status)
     quote = Quote.new(
       quoted_status: quoted_status,