public CircuitBreakerRpcClient build(RpcClient delegate) {
        return new CircuitBreakerRpcClient(delegate, handler(), ruleWithContent(), fallback());
    }
Returns a newly-created {@link CircuitBreakerRpcClient} based on the properties of this builder.
core/src/main/java/com/linecorp/armeria/client/circuitbreaker/CircuitBreakerRpcClientBuilder.java