Allow for notification settings for recsys email

Closes https://gitlab.com/JOGL/JOGL/-/issues/722 Reset your database with bundle exec rails db:reset

To test make sure you have redis, maildev, and sidekiq running.

RecsysMailerWorker.perform_async() you'll see one recommendation email.

user = User.find(1)
user.settings.categories!.recsys!.delivery_methods!.email!.enabled = false
user.save

RecsysMailerWorker.perform_async() you won't get an email.

user.settings.categories!.recsys!.delivery_methods!.email!.enabled = true
user.save

RecsysMailerWorker.perform_async() you'll get another email.