Send email notifying user he has been unsubscribed.

app/controllers/unsubscribes_controller.rb

@@ -10,7 +10,10 @@ class UnsubscribesController < ApplicationController
 
   def create
     @user = get_user
-    @user.admin_unsubscribe! if @user
+    if @user
+      @user.admin_unsubscribe!
+      Notify.send_unsubscribed_notification(@user).deliver
+    end
     redirect_to new_user_session_path, notice: 'You have been unsubscribed'
   end
 

app/mailers/emails/admin_notification.rb

@@ -6,5 +6,10 @@ module Emails
       @body = body
       mail to: email, subject: subject
     end
+
+    def send_unsubscribed_notification(user_id)
+      email = recipient(user_id)
+      mail to: email, subject: "Unsubscribed from GitLab administrator notifications"
+    end
   end
 end