Add powerdns configuration API as resources

[selfuryon]

Hi!

I want to add recursor/auth configuration (it's the same one exists for auth server but not shown in docs) as resource to this provider.

I think I can add it like this:

resource "powerdns_configuration" "root" {
    name = "allow-from",                    #string
    type = "ConfigSetting",                 #string
    value = "127.0.0.0/8, 10.0.0.0/8"       #string
}