```ruby
require 'base64'
require 'openssl'

module Carto
  class GoogleMapsApiSigner
    def initialize(user)
      @user = user
    end

    def sign(url)
      raise 'User does not have Google configured' unless @user.google_maps_query_string.present?
      url_with_qs = "#{url}&#{@user.google_maps_query_string}"
      if @user.google_maps_client_id.present? && @user.google_maps_private_key.present?
        # Add client=xxx + signature
        cryptographically_sign_url(url_with_qs)
      else
        # Just add key=xxx
        url_with_qs
      end
    end

    private

    def cryptographically_sign_url(url)
      binary_signature = hmac(uri_path_and_query(url))
      signature = Base64.urlsafe_encode64(binary_signature)

      "#{url}&signature=#{signature}"
    end

    def uri_path_and_query(url)
      uri = URI.parse(url)
      uri.path + '?' + uri.query
    end

    def hmac(data)
      OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha1'), binary_key, data)
    end

    def binary_key
      Base64.urlsafe_decode64(@user.google_maps_private_key)
    end
  end
end
```

Refactor Google Maps Api Signer
user
```ruby
require 'base64'
require 'openssl'

module Carto
  class GoogleMapsApiSigner
    def sign(user, url)
      raise 'User does not have Google configured' unless user.google_maps_query_string.present?
      if user.google_maps_client_id.present? && user.google_maps_private_key.present?
        # Add client=xxx + signature
        client_id_signed_url(user, url)
      else
        # Just add key=xxx
        key_signed_url(user, url)
      end
    end

    private

    def client_id_signed_url(user, url)
      uri = URI.parse(url)
      payload_to_sign = uri.path + '?' + uri.query
      signature = hmac(user.google_maps_private_key, payload_to_sign)

      "#{url}&#{user.google_maps_query_string}&signature=#{signature}"
    end

    def key_signed_url(user, url)
      "#{url}&#{user.google_maps_query_string}"
    end

    def hmac(key, data)
      binary_key = Base64.urlsafe_decode64(key)
      binary_signature = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha1'), binary_key, data)
      Base64.urlsafe_encode64(binary_signature)
    end
  end
end
```
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