Version bump, Style guide, dns records updates optional, and input validation

variable.host_name.tf

@@ -1,4 +1,10 @@
 variable "host_name" {
-  default = "hello-world"
-  type    = string
+  default     = "hello-world"
+  description = "The host name for the Linode instance."
+  type        = string
+
+  validation {
+    condition     = can(regex("^[a-zA-Z0-9-]+$", var.host_name))
+    error_message = "The host name can only contain alphanumeric characters and hyphens."
+  }
 }