:raised_hands: Add support for multiple sidekiqs

This is so we can have iHat and tahi running on the same machine without one sidekiq fighting over the other.

Make sure to have `REDIS_PROVIDER` set in your .env.
Good point. 

I will try removing the `url` key first. I don't see why it won't work.

Though if that doesn't work, I am thinking of dropping `REDIS_PROVIDER` in favor of `ENV['REDIS_URL'] || ENV['REDISCLOUD_URL']`. Makes sense. 

`REDIS_URL` is the conventional configuration environment variable. Sidekiq also looks for it under the hood.