adds email digest for proposal notifications

app/mailers/mailer.rb

@@ -59,6 +59,14 @@ class Mailer < ApplicationMailer
     end
   end
 
+  def proposal_notification_digest(user)
+    @notifications = user.notifications.where(notifiable_type: "ProposalNotification")
+
+    with_user(user) do
+      mail(to: user.email, subject: "Email digest")
+    end
+  end
+
   private
 
   def with_user(user, &block)