refactors proposal_notification.public_for_api

app/models/proposal_notification.rb

@@ -1,7 +1,7 @@
 class ProposalNotification < ActiveRecord::Base
 
   include Graphqlable
-  
+
   belongs_to :author, class_name: 'User', foreign_key: 'author_id'
   belongs_to :proposal
 
@@ -10,7 +10,7 @@ class ProposalNotification < ActiveRecord::Base
   validates :proposal, presence: true
   validate :minimum_interval
 
-  scope :public_for_api, ->  { joins(:proposal).where("proposals.hidden_at IS NULL") }
+  scope :public_for_api, -> { where(proposal_id: Proposal.public_for_api.pluck(:id)) }
 
   def minimum_interval
     return true if proposal.try(:notifications).blank?