Merge branch 'add-liked' into 'master'

add liked in collection serializer and collection min serializer

See merge request !341

app/serializers/collection_min_serializer.rb

 class CollectionMinSerializer < ActiveModel::Serializer
-  cache key: 'collection', expires_in: 4.hours
-  attributes :id, :name, :owner, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :review_average, :thumbnail
+  cache key: 'collection', expires_in: 4.hours, except: [:likes_count, :liked]
+
+  def liked
+    object.liked? current_user
+  end
+
+
+  attributes :id, :name, :owner, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :review_average, :thumbnail
   has_many :tags
   has_many :subjects
   has_many :educational_stages

app/serializers/collection_serializer.rb

 class CollectionSerializer < ActiveModel::Serializer
-  cache key: 'collection', expires_in: 4.hours
-  attributes :id, :name, :owner, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :review_average, :thumbnail
+  cache key: 'collection', expires_in: 4.hours, except: [:likes_count, :liked]
+
+  def liked
+    object.liked? current_user
+  end
+
+  attributes :id, :name, :owner, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :review_average, :thumbnail
   has_many :tags
   has_many :subjects
   has_many :educational_stages