* Refactor controller validations to model
* Update specs and move current email validation back
* Refactor #subscribed
* Cleanup UserSubscriptions::Create service
* Refactor service
* Move source inside of call for clarity
* Specs for UserSubscription::Create
* Cleanup spec
* Fix Article spec
* Updated for subscriber_email
* Add comment for explicitness of subscriber_email
* Fix reference in comment...oops!
* I know what I'm doing...sometimes...maybe
* Rename CachChecker - Subscription to IsSubscribed
* Use include vs eq in specs for error messages
* attr_accessor --> attr_reader
* Don't explicitly set nil
* Rename Create service to CreateFromService
* Use errors_as_sentence
* Rename service to CreateFromControllerParams
* Assign Struct to a new constant
* Add migrations for subscriber_email column
* Add new schema
* Update relationships, specs, and factory
* Use unless index_exists? over if !index_exists?
* Fix typo in last fix for migration
* Rename authored_user_subscriptions
- to source_authored_user_subcriptions
* Add factory methods and specs
- UserSubscription.make
- UserSubscription.make_new
- Article.new_user_subscription
- Article.create_user_subscription
* Remove self and &
* Change make_new to build
* new_user_subscription --> build_user_subscription
* Come on, Travis
