* Dont use raise_error by itself (avoids warning)

* Add coverage for AccountFilter

* Improve coverage and refactor for Subscription#lease_seconds

* Improve coverage and refactor for NotificationMailer

* Simplify assignment of min/max threshold on subscription

* Fix subscription expiration condition

* dry and add spec

* add annotate to Gemfile

* rails g annotate:install

* configure annotate_models

* add schema info to models

* fix rubocop to add frozen_string_literal

* Add `required: true` option to foreign column

* Fixes NoMethodError

```
> Favourite.new.valid?
NoMethodError: undefined method `reblog?' for nil:NilClass
```