add support to spark.redis.url

[jonathansp]

Since redis 4.0, redis-cli accepts -u parameter, where an URL can be provided. Redis URL scheme is a well-known format (https://www.iana.org/assignments/uri-schemes/prov/redis) supported by most Redis drivers.

# snippet from redis-py.

>>> from redis.cluster import RedisCluster as Redis
>>> rc = Redis.from_url("redis://localhost:6379/0")

// snippet from jedis.

Jedis jedis = new Jedis("redis://:password@host:port/database");

Since spark-redis uses Jedis, I'd like to suggest adding support to spark.redis.url to connect to Redis.

References:

• https://www.iana.org/assignments/uri-schemes/prov/redis
• https://github.com/redis/redis-py
• https://github.com/RedisLabs/spark-redis/blob/master/pom.xml#L52