Fix creating exercise collections with exercises

app/controllers/exercise_collections_controller.rb

@@ -17,9 +17,10 @@ class ExerciseCollectionsController < ApplicationController
   end
 
   def create
-    @exercise_collection = ExerciseCollection.new(exercise_collection_params)
+    @exercise_collection = ExerciseCollection.new
     authorize!
-    create_and_respond(object: @exercise_collection)
+    @exercise_collection.save
+    update_and_respond(object: @exercise_collection, params: exercise_collection_params)
   end
 
   def destroy
@@ -31,6 +32,7 @@ class ExerciseCollectionsController < ApplicationController
   end
 
   def update
+    authorize!
     update_and_respond(object: @exercise_collection, params: exercise_collection_params)
   end
 

app/models/exercise.rb

@@ -15,7 +15,7 @@ class Exercise < ActiveRecord::Base
   has_and_belongs_to_many :proxy_exercises
   has_many :user_proxy_exercise_exercises
   has_many :exercise_collection_items
-  has_many :exercise_collections, through: :exercise_collection_items
+  has_many :exercise_collections, through: :exercise_collection_items, inverse_of: :exercises
   has_many :user_exercise_interventions
   has_many :interventions, through: :user_exercise_interventions
   has_many :exercise_tags

app/models/exercise_collection.rb

@@ -3,7 +3,7 @@ class ExerciseCollection < ActiveRecord::Base
 
   has_many :exercise_collection_items
   alias_method :items, :exercise_collection_items
-  has_many :exercises, through: :exercise_collection_items
+  has_many :exercises, through: :exercise_collection_items, inverse_of: :exercise_collections
   belongs_to :user, polymorphic: true
 
   def collection_statistics