You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: configuration.rb
    path of file: ./repos/vets-api/lib/lighthouse/veteran_verification
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require 'common/client/configuration/rest'
require 'faraday/multipart'
require 'lighthouse/auth/client_credentials/jwt_generator'
require 'l
    
    def token_service(lighthouse_client_id, lighthouse_rsa_key_path, aud_claim_url = nil, host = nil)
      # default client id and rsa key is used from the form526 block
      lighthouse_client_id = settings.form526.access_token.client_id if lighthouse_client_id.nil?
      lighthouse_rsa_key_path = settings.form526.access_token.rsa_key if lighthouse_rsa_key_path.nil?

      host ||= base_path(host)
      url = "#{host}/#{TOKEN_PATH}"
      aud_claim_url ||= settings.aud_claim_url

      @token_service ||= Auth::ClientCredentials::Service.new(
        url, API_SCOPES, lighthouse_client_id, aud_claim_url, lighthouse_rsa_key_path, 'veteran-verification'
      )
    end