How to customize id_generator or storage in Rails?

Customization examples are only given for Sinatra. How do achieve the same in Rails?

```ruby
    id_generator = proc do
      SecureRandom.base36(24) # Roughly the same as 2^128
    end
    config.middleware.use 'Rack::RequestId',
      id_generator: id_generator,
      storage: RequestStore
```
