Merge branch 'collection_thumbnail' into 'master'

modify collection serializer to return first 4 items' thumbnails

See merge request !362

app/models/collection_item.rb

@@ -24,4 +24,9 @@ class CollectionItem < ApplicationRecord
   def recipient
     collection
   end
+
+  def thumbnail
+    collectionable_type == 'LearningObject' ?  LearningObject.find(collectionable_id).default_thumbnail : Collection.find(collectionable_id).thumbnail
+  end
+
 end

app/serializers/collection_serializer.rb

@@ -13,7 +13,15 @@ class CollectionSerializer < ActiveModel::Serializer
     object.complained? current_user
   end
 
-  attributes :id, :name, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :reviewed, :complained, :review_average, :thumbnail
+  def items_thumbnails
+    thumbs = []
+    object.collection_items[0..3].each do | t |
+      thumbs << t.thumbnail
+    end
+    thumbs
+  end
+
+  attributes :id, :name, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :reviewed, :complained, :review_average, :thumbnail, :items_thumbnails
   belongs_to :owner
   has_many :tags
   has_many :subjects