Change unauthenticated responses to be cached in REST API (#24348)

app/controllers/api/v1/instances/extended_descriptions_controller.rb

@@ -5,8 +5,10 @@ class Api::V1::Instances::ExtendedDescriptionsController < Api::BaseController
 
   before_action :set_extended_description
 
+  vary_by ''
+
   def show
-    expires_in 3.minutes, public: true
+    cache_even_if_authenticated!
     render json: @extended_description, serializer: REST::ExtendedDescriptionSerializer
   end