Simplify server and agent definition for kubernetes

The definition was split into multiple settings, that made it
unnecessary complicated to setup the definition for my kubernetes
cluster. This new approach allows for granular definitions of servers
and agents and is also simpler to use for me.

main.tf

@@ -9,16 +9,8 @@ module "k8s" {
 
   name     = "cluster1"
   ssh_keys = [for o in hcloud_ssh_key.this : o.id]
-  servers = [for n in range(var.k8s_server_count) : {
-    type          = var.k8s_server_type
-    location      = var.k8s_location
-    ip_datacenter = var.k8s_ip_datacenter
-  }]
-  agents = [{
-    type     = var.k8s_agent_type
-    location = var.k8s_location
-    count    = var.k8s_agent_count
-  }]
+  servers = var.k8s_servers
+  agents = var.k8s_agents
   auto_delete_primary_ips = false
   kubernetes_exposed_ips  = var.kubernetes_allowed_ips
   ssh_exposed_ips         = var.ssh_allowed_ips

variables.tf

@@ -20,45 +20,32 @@ variable "ssh_keys" {
   type = map(string)
 }
 
-# Right now this only supports 1 location, but that's okay for me!
-variable "k8s_location" {
-  type        = string
+variable "k8s_servers" {
+  type = list(object({
+    type          = optional(string, "cax11")
+    location      = string
+    ip_datacenter = string
+  }))
   description = <<EOF
-  This is the location where I host the k8s-cluster.
-  An overview of possible locations can be found at: https://docs.hetzner.com/cloud/general/locations/
+  The servers of the kubernetes-cluster.
+  This should always contain an off number of servers.
+  An overview of locations can be found at: https://docs.hetzner.com/cloud/general/locations/
+  Note, that the ip_datacenter has to match the location.
   EOF
 }
 
-variable "k8s_ip_datacenter" {
-  type        = string
+variable "k8s_agents" {
+  type = list(object({
+    type     = optional(string, "cax11")
+    location = string
+    count    = optional(number, 1)
+  }))
   description = <<EOF
-  This is the datacenter where the public IPs of the k8s-cluster belong to.
-  An overview of possible locations can be found at: https://docs.hetzner.com/cloud/general/locations/
-  Note, that the k8s_ip_datacenter has to match the k8s_location!
+  The agents of the kubernetes-cluster.
+  An overview of locations can be found at: https://docs.hetzner.com/cloud/general/locations/
   EOF
 }
 
-variable "k8s_server_count" {
-  type        = number
-  default     = 3
-  description = "Number of k8s-server nodes. This should always be an odd number."
-}
-
-variable "k8s_server_type" {
-  type    = string
-  default = "cax11"
-}
-
-variable "k8s_agent_count" {
-  type    = number
-  default = 3
-}
-
-variable "k8s_agent_type" {
-  type    = string
-  default = "cax11"
-}
-
 variable "dns_zones" {
   type = map(object({
     zone_ttl = optional(number, 900)