static void validateFallbackFactory(final Class clazz) {
        Assert.isTrue(!clazz.isInterface(), "Fallback factory must produce instances "
                + "of fallback classes that implement the interface annotated by @ShenyuClient");
    }
Validate fallback factory.

@param clazz the clazz
shenyu-sdk/shenyu-sdk-spring/src/main/java/org/apache/shenyu/sdk/spring/ShenyuClientsRegistrar.java