def base64_url_decode(str)
      encoded_str = str.tr('-_', '+/')
      encoded_str += '=' while !(encoded_str.size % 4).zero?
      Base64.decode64(encoded_str)
    end
def base64_url_decode(str)
      encoded_str = str.tr('-_', '+/')
      encoded_str += '=' while !(encoded_str.size % 4).zero?
      Base64.decode64(encoded_str)
    end
Decode a base64URL encoded string: replace - with + and _ with /
 Also add padding so ruby's Base64 can decode it
 @return [String] the plain string decoded