Add Redis config option number_of_databases

[LachlanArthur]

This PR adds support for the DO database cluster config option redis_number_of_databases via the argument number_of_databases:

resource "digitalocean_database_cluster" "foobar" {
  engine              = "redis"
  ...
  number_of_databases = 128
}

[andrewsomething]

Hi @LachlanArthur!

Thanks for this great contribution.

The DigitalOcean API has grown a lot of additional configuration options that are specific to the individual database engines. As we add support for more here, I'm afraid that we'll be overloading the digitalocean_database_cluster resource with options that are only relevant to sub-sets of users and making it more difficult to maintain moving forward.

For instance with Redis, there are more options that we will likely want to add than just number_of_databases:

https://github.com/digitalocean/godo/blob/3a26e25b76a419426decf9c9f1e0c1b45c9e06b2/databases.go#L504-L516

I'm thinking that it might make more sense to create a new digitalocean_redis_configuration (or similar) resource to hold all of these options rather than further extending the base database resource.

[andrewsomething]

Hi @LachlanArthur,

I've implemented the approach I suggested in a new PR: #1037 It supports the number_of_databases as well as all the other options exposed by that endpoint.

Let me if you have any feedback on that PR, and thanks for starting the conversation on how we can support these options in the Terraform provider.