Make every important setting of the k8s-cluster configurable

This change makes all the settings configurable. The only part which
still lacks some flexibility is the location, though I really don't need
to run a k8s-cluster over multiple datacenters and regions! - At least
right now ;-)

variables.tf

@@ -25,3 +25,50 @@ variable "ssh_keys" {
   type = map(string)
 }
 
+variable "k8s_test_installation" {
+  default     = false
+  description = <<EOF
+  When this is set to true we configure primary-ips to not be deleted automatically!
+  This allows us to reuse the same IP for multiple create/destroy cycles.
+  As soon as the test-phase is over this should be false.
+  EOF
+}
+
+# Right now this only supports 1 location, but that's okay for me!
+variable "k8s_location" {
+  type        = 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/
+  EOF
+}
+
+variable "k8s_ip_datacenter" {
+  type        = string
+  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!
+  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"
+}