Fix azure provider warning, rename a public_ip field

* azurerm_public_ip (used internally) added a field `allocation_method`
to replace the field `public_ip_address_allocation` (deprecated)
* Require terraform-provider-azurerm v1.21+
* https://github.com/terraform-providers/terraform-provider-azurerm/pull/2576

CHANGES.md

@@ -14,6 +14,11 @@ Notable changes between versions.
 
 * Add `ingress_zone_id` output with the NLB DNS name's Route53 zone for use in alias records ([#380](https://github.com/poseidon/typhoon/pull/380))
 
+#### Azure
+
+* Fix azure provider warning, `public_ip` `allocation_method` replaces `public_ip_address_allocation`
+  * Require `terraform-provider-azurerm` v1.21+ (action required)
+
 #### Addons
 
 * Update nginx-ingress from v0.21.0 to v0.22.0

azure/container-linux/kubernetes/controllers.tf

@@ -124,7 +124,7 @@ resource "azurerm_public_ip" "controllers" {
   name              = "${var.cluster_name}-controller-${count.index}"
   location          = "${azurerm_resource_group.cluster.location}"
   sku               = "Standard"
-  public_ip_address_allocation = "static"
+  allocation_method = "Static"
 }
 
 # Controller Ignition configs

azure/container-linux/kubernetes/lb.tf

@@ -20,7 +20,7 @@ resource "azurerm_public_ip" "apiserver-ipv4" {
   name              = "${var.cluster_name}-apiserver-ipv4"
   location          = "${var.region}"
   sku               = "Standard"
-  public_ip_address_allocation = "static"
+  allocation_method = "Static"
 }
 
 # Static IPv4 address for the ingress frontend
@@ -30,7 +30,7 @@ resource "azurerm_public_ip" "ingress-ipv4" {
   name              = "${var.cluster_name}-ingress-ipv4"
   location          = "${var.region}"
   sku               = "Standard"
-  public_ip_address_allocation = "static"
+  allocation_method = "Static"
 }
 
 # Network Load Balancer for apiservers and ingress

azure/container-linux/kubernetes/require.tf

@@ -5,7 +5,7 @@ terraform {
 }
 
 provider "azurerm" {
-  version = "~> 1.19"
+  version = "~> 1.21"
 }
 
 provider "local" {