def in_to_at(expires_in)
      if expires_in.to_i < 1
        0
      else
        Time.now.utc.to_i + expires_in.to_i
      end
    end
def in_to_at(expires_in)
      if expires_in.to_i < 1
        0
      else
        Time.now.utc.to_i + expires_in.to_i
      end
    end
Convert expires_in into expires_at

 @param [Fixnum] seconds_till_expiration
 @return [Fixnum] expires_at_unix_timestamp