Refactor Cache-Control and Vary definitions (#24347)

app/controllers/admin/base_controller.rb

@@ -8,6 +8,8 @@ module Admin
     layout 'admin'
 
     before_action :set_body_classes
+    before_action :set_cache_headers
+
     after_action :verify_authorized
 
     private
@@ -16,6 +18,10 @@ module Admin
       @body_classes = 'admin'
     end
 
+    def set_cache_headers
+      response.cache_control.replace(private: true, no_store: true)
+    end
+
     def set_user
       @user = Account.find(params[:account_id]).user || raise(ActiveRecord::RecordNotFound)
     end