collections can add and remove educational_stages separately

app/controllers/v1/collections_controller.rb

@@ -5,11 +5,13 @@ class V1::CollectionsController < ApplicationController
   include ::DeletedObjectsController
   include ::HighlightsController
   include ::Paginator
+  include ::SubjectableController
+  include ::StageableController
 
   before_action :authenticate_user!, only: [:create, :update, :destroy]
   before_action :set_collection, only: [:show, :update, :destroy, :add_object, :delete_object]
   before_action :set_new_collection, only: :index
-  before_action :authorize!, except: [:create, :tagging, :untagging]
+  before_action :authorize!, except: [:create, :tagging, :untagging, :subjecting, :unsubjecting, :add_stages, :remove_stages]
 
   # GET /v1/collections
   # GET /v1/collections.json
@@ -81,6 +83,8 @@ class V1::CollectionsController < ApplicationController
   def followable; set_collection; end
   def taggable; set_collection; end
   def sociable; set_collection; end
+  def subjectable; set_learning_object; end
+  def stageable; set_learning_object; end
 
   def set_collection
     @collection ||= Collection.find(params[:id])