nxt_clients_user_fetcher.rb

class UserService::Api::UserFetcher < ::NxtClients::Client
  configure do |config|
    config.base_url = user_service_base_url
    config.request_options.deep_merge!(headers: headers)
  end
  
  def call
    fire("/users/#{user_id}") do |response_handler|
      response_handler.on(:success) do |response|
        json = JSON(response.body)
        UserService::User.new(json)
      end
    end
  end
  
  ...
end