private static boolean isMatchAll(final String key) {
        return MATCH_ALL.equals(key);
    }
match all, when the path is /ab/c/**, that means /a/b/c/d can be matched.

@param key key
@return match result
shenyu-plugin/shenyu-plugin-base/src/main/java/org/apache/shenyu/plugin/base/trie/ShenyuTrie.java