contrib/go-redis/redis.v8: support wrapping a go-redis v8 client

[seancaffery]

The current redis-go v8 integration only supports a regular Redis client. I'd like to add support for adding a hook to an existing UniversalClient so I can add a tracing hook to a FailOverClient.

The API would be similar to the one provided for the previous redis-go integration. Something like:

func WrapClient(c redis.UniversalClient, opts ...ClientOption) redis.UniversalClient {
  // set up client
  // add hook
  // return client
}

We can likely share much of the code from NewClient.

An alternative could be to change NewClient to accept redis.UniversalOptions but that would be a breaking change and I imagine would be more difficult to roll out.

[knusbaum]

👍 This looks like something we want to support.

We should be careful to consider any differences (things worth making into tags, etc.) between the UniversalClient compared to the regular Client.

[seancaffery]

I've created #808. It'd be great to get your thoughts on how we should handle tags for each kind of client.