@Override
  public String set(String key, String value) {
    return execute((jedis -> jedis.set(redisKeyPrefix + key, value)));
  }
Default implementation for {@link JedisTaskExecutor} which is the Jedis wrapper used to access
Redis.

TODO(zheng): support redis cluster.
src/main/java/com/eudemon/ratelimiter/redis/DefaultJedisTaskExecutor.java