private static TokenRequestException onBadRequestError(AggregatedHttpResponse errorResponse) {
        return TokenRequestException.parse(errorResponse.contentUtf8());
    }
Composes {@link TokenRequestException} upon 400 Bad Request response
as per <a href="https://datatracker.ietf.org/doc/html/rfc6749#section-5.2">[RFC6749], Section 5.2</a>.

@param errorResponse response received from the server

@return an instance of {@link TokenRequestException}
oauth2/src/main/java/com/linecorp/armeria/internal/common/auth/oauth2/AbstractOAuth2ResponseHandler.java