Add exclusive lists (#22048)

Co-authored-by: Liam Cooke <liam@liamcooke.com>
Co-authored-by: John Holdun <john@johnholdun.com>
Co-authored-by: Effy Elden <effy@effy.space>
Co-authored-by: Lina Reyne <git@lina.pizza>
Co-authored-by: Lina <20880695+necropolina@users.noreply.github.com>
Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/controllers/api/v1/lists_controller.rb

@@ -42,6 +42,6 @@ class Api::V1::ListsController < Api::BaseController
   end
 
   def list_params
-    params.permit(:title, :replies_policy)
+    params.permit(:title, :replies_policy, :exclusive)
   end
 end