Rails 6.0 clamps down on dangerous query methods

[jaysonvirissimo]

DEPRECATION WARNING: Dangerous query method (method whose arguments are used as raw SQL) called with non-attribute argument(s): "random()". 
Non-attribute arguments will be disallowed in Rails 6.0. 
This method should not be called with user-provided values, such as request parameters or model attributes. 
Known-safe values can be passed by wrapping them in Arel.sql().

The offending code was found in lib/okubo/models/deck.rb:46.