code: public static final AuthToken consumeToken(String encodedJson) throws IllegalArgumentException {
          String json = StringUtils.newStringUtf8(Base64.decodeBase64(encodedJson));
          AuthToken token = fromJSON(json);
          validateToken(token);
          return token;
      }
docs: Consumes an auth token, validating it during the process.  If successful, the
  {@link AuthToken} is returned.  If the token is invalid (expired or bad
  signature) then an {@link IllegalArgumentException} is thrown.  Any other
  error will result in a runtime exception.
  @param encodedJson the raw token
  @return the token
  @throws IllegalArgumentException indicate that a method has been passed an
  illegal or inappropriate argument