public AuthServiceBuilder onFailure(AuthFailureHandler failureHandler) {
        this.failureHandler = requireNonNull(failureHandler, "failureHandler");
        return this;
    }
Sets the {@link AuthFailureHandler} which handles the requests with failed authorization.
By default, an exception thrown during authorization is logged at WARN level (if any) and a
{@code 401 Unauthorized} response will be sent.
core/src/main/java/com/linecorp/armeria/server/auth/AuthServiceBuilder.java