Extended Exercises by worktime, difficulty and tags, added ProxyExercises as prework for recommendations

Tags can be added to exercises in the edit view. Tags can monitored under /tags.
Added the concept of ProxyExercises which are a collection of Exercises. They can be found under /proxy_exercises
Added Interventions as prework to show interventions later to the user.
Added exercise/[:id]/working_time to return the working time of the user in this exercise and the average working time of all users in this exercise

app/controllers/proxy_exercises_controller.rb

@@ -0,0 +1,80 @@
+class ProxyExercisesController < ApplicationController
+  include CommonBehavior
+
+  before_action :set_exercise, only: MEMBER_ACTIONS + [:clone, :reload]
+
+  def authorize!
+    authorize(@proxy_exercise || @proxy_exercises)
+  end
+  private :authorize!
+
+  def clone
+    proxy_exercise = @proxy_exercise.duplicate(token: nil, exercises: @proxy_exercise.exercises)
+    proxy_exercise.send(:generate_token)
+    if proxy_exercise.save
+      redirect_to(proxy_exercise, notice: t('shared.object_cloned', model:  ProxyExercise.model_name.human))
+    else
+      flash[:danger] = t('shared.message_failure')
+      redirect_to(@proxy_exercise)
+    end
+  end
+
+  def create
+    myparams = proxy_exercise_params
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.empty? })
+    @proxy_exercise = ProxyExercise.new(myparams)
+    authorize!
+
+    create_and_respond(object: @proxy_exercise)
+  end
+
+  def destroy
+    destroy_and_respond(object: @proxy_exercise)
+  end
+
+  def edit
+    @search = policy_scope(Exercise).search(params[:q])
+    @exercises = @search.result.order(:title)
+    authorize!
+  end
+
+  def proxy_exercise_params
+    params[:proxy_exercise].permit(:description, :title, :exercise_ids  => [])
+  end
+  private :proxy_exercise_params
+
+  def index
+    @search = policy_scope(ProxyExercise).search(params[:q])
+    @proxy_exercises = @search.result.order(:title).paginate(page: params[:page])
+    authorize!
+  end
+
+  def new
+    @proxy_exercise =  ProxyExercise.new
+    @search = policy_scope(Exercise).search(params[:q])
+    @exercises = @search.result.order(:title)
+    authorize!
+  end
+
+  def set_exercise
+    @proxy_exercise = ProxyExercise.find(params[:id])
+    authorize!
+  end
+  private :set_exercise
+
+  def show
+    @search = @proxy_exercise.exercises.search
+    @exercises = @proxy_exercise.exercises.search.result.order(:title) #@search.result.order(:title)
+  end
+
+  #we might want to think about auth here
+  def reload
+  end
+
+  def update
+    myparams = proxy_exercise_params
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.blank? })
+    update_and_respond(object: @proxy_exercise, params: myparams)
+  end
+
+end