I have been working on Ruby Gem for interacting with Rasa Core. This gem allows a ruby developer to interact with a core server without worrying about details of HTTP API. This is the GitHub page of the gem, and this is the Rubygem page. I have also created a simple Ruby-On-Rails application to chat with a bot from the Rails application.
I am planning to add more functionalities and work on this gem further, so your feedbacks, suggestions, and opinions are valuable.