added pick_host_name_from_backend_http_settings and host_name

azurerm/modules/azurerm-app-gateway/app_gateway.tf

@@ -101,12 +101,13 @@ resource "azurerm_application_gateway" "network" {
 
   probe {
     name                = "k8s-probe"
-    host                = "127.0.0.1"
+    host                = var.pick_host_name_from_backend_http_settings ? null : "127.0.0.1"
     protocol            = "Http"
     interval            = 15
     unhealthy_threshold = 4
     timeout             = 15
     path                = "/healthz"
+    pick_host_name_from_backend_http_settings = var.pick_host_name_from_backend_http_settings 
     match {
       status_code = ["200"]
     }
@@ -119,6 +120,7 @@ resource "azurerm_application_gateway" "network" {
     protocol              = "Http"
     request_timeout       = 10
     probe_name            = "k8s-probe"
+    host_name             = var.host_name
   }
 
   request_routing_rule {

azurerm/modules/azurerm-app-gateway/vars.tf

@@ -185,3 +185,15 @@ variable "acme_email" {
   type        = string
   description = "Email for Acme registration, must be a valid email"
 }
+
+variable "pick_host_name_from_backend_http_settings" {
+  type        = bool
+  default     = false
+  description = "Whether the host header should be picked from the backend HTTP settings. Defaults to false."
+}
+
+variable "host_name" {
+  type        = string
+  default     = null
+  description = "Host header to be sent to the backend servers. Cannot be set if pick_host_name_from_backend_address is set to true"
+}