[Improvement] Option for multiget values

[jarussi]

Describe the improvement

I think it would be a nice feature to have the option to use the mget method that both backends already implements inside the config.
We have several cases where we call a few keys in the same operation. If we could make a single request (in our cause to redis), it would decrease our hits to redis by a lot.

Think it's a valid idea? The hardest part (the implementation of mget itself on both backends) is already done. Just would need to let the method visible inside the Config.