some_controller.rb

class SomeController < ApplicationController
  # params either looks like...
  #   params = { login: { email: "foo@example.com", password: "bar" } }
  #   params = { new_user: { email: "foo@example.com", full_name: "Soo Moo", password: "bar" } }
  def some_endpoint
    @user = User::SignupOrLoginService.new(params, request.remote_ip).auth
    render json: @user
  end
end