Notice model should have attribute status: true initially.
Include ActiveModel::Serializers::JSON in Notice so it can use #as_json.
User always has a Notice.

If no Notice is saved in Redis, one is instantiated. Since a Notice only has on and off states, by default that state is off and we can assume it will be off until it is on--at which point a Redis backed record will be saved.
Add controller RSpec tests.