add ARM template for onboarding clusters in AKS

examples/aks/aks_cluster_arm_template/README.MD

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+# AKS and CAST AI example with CAST AI Autoscaler policies and additional Node Configurations
+Following example shows how to onboard AKS cluster to CAST AI, configure [Autoscaler policies](https://docs.cast.ai/reference/policiesapi_upsertclusterpolicies) and additional [Node Configurations](https://docs.cast.ai/docs/node-configuration/).
+
+Example configuration should be analysed in the following order:
+1. Create Virtual network - `vnet.tf`
+2. Create AKS cluster - `aks.tf`
+3. Create CAST AI related resources to connect AKS cluster to CAST AI, configure Autoscaler and Node Configurations - `castai.tf`
+
+# Usage
+1. Rename `tf.vars.example` to `tf.vars`
+2. Update `tf.vars` file with your cluster name, cluster region and CAST AI API token.
+3. Initialize Terraform. Under example root folder run:
+```
+terraform init
+```
+4. Run Terraform apply:
+```
+terraform apply -var-file=tf.vars
+```
+5. To destroy resources created by this example:
+```
+terraform destroy -var-file=tf.vars
+```

examples/aks/aks_cluster_arm_template/aks.tf

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+# 2. Create AKS cluster.
+
+resource "azurerm_kubernetes_cluster" "this" {
+  name                = var.cluster_name
+  resource_group_name = azurerm_resource_group.this.name
+  location            = azurerm_resource_group.this.location
+  dns_prefix          = var.cluster_name
+  node_resource_group = "${var.cluster_name}-ng"
+
+  default_node_pool {
+    name           = "default"
+    # Node count has to be > 2 to successfully deploy CAST AI controller.
+    node_count     = 2
+    vm_size        = "Standard_D2_v2"
+    vnet_subnet_id = azurerm_subnet.internal.id
+  }
+
+  identity {
+    type = "SystemAssigned"
+  }
+
+  tags = {
+    Environment = "Test"
+  }
+}

examples/aks/aks_cluster_arm_template/castai.tf

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+# 3. Connect AKS cluster to CAST AI in READ-ONLY mode.
+
+# Configure Data sources and providers required for CAST AI connection.
+data "azurerm_subscription" "current" {}
+
+provider "castai" {
+  api_url   = var.castai_api_url
+  api_token = var.castai_api_token
+}
+
+provider "helm" {
+  kubernetes {
+    host                   = azurerm_kubernetes_cluster.this.kube_config.0.host
+    client_certificate      = base64decode(azurerm_kubernetes_cluster.this.kube_config.0.client_certificate)
+    client_key             = base64decode(azurerm_kubernetes_cluster.this.kube_config.0.client_key)
+    cluster_ca_certificate  = base64decode(azurerm_kubernetes_cluster.this.kube_config.0.cluster_ca_certificate)
+  }
+}
+
+# Configure AKS cluster connection to CAST AI using CAST AI aks-cluster module.
+module "castai-aks-cluster" {
+  source = "castai/aks/castai"
+
+  api_url                = var.castai_api_url
+  castai_api_token       = var.castai_api_token
+  wait_for_cluster_ready = true
+
+  aks_cluster_name    = var.cluster_name
+  aks_cluster_region  = var.cluster_region
+  node_resource_group = azurerm_kubernetes_cluster.this.node_resource_group
+  resource_group      = azurerm_kubernetes_cluster.this.resource_group_name
+
+  delete_nodes_on_disconnect = var.delete_nodes_on_disconnect
+
+  subscription_id = data.azurerm_subscription.current.subscription_id
+  tenant_id       = data.azurerm_subscription.current.tenant_id
+
+  default_node_configuration = module.castai-aks-cluster.castai_node_configurations["default"]
+
+  node_configurations = {
+    default = {
+      disk_cpu_ratio  = 25
+      subnets         = [azurerm_subnet.internal.id]
+      tags            = var.tags
+    }
+
+    test_node_config = {
+      disk_cpu_ratio  = 25
+      subnets         = [azurerm_subnet.internal.id]
+      tags            = var.tags
+      max_pods_per_node = 40
+    }
+  }
+
+  node_templates = {
+    default_by_castai = {
+      name = "default-by-castai"
+      configuration_id = module.castai-aks-cluster.castai_node_configurations["default"]
+      is_default   = true
+      should_taint = false
+
+      constraints = {
+        on_demand          = true
+        spot               = true
+        use_spot_fallbacks = true
+
+        enable_spot_diversity                       = false
+        spot_diversity_price_increase_limit_percent = 20
+      }
+    }
+    spot_tmpl = {
+      configuration_id = module.castai-aks-cluster.castai_node_configurations["default"]
+      should_taint = true
+
+      custom_labels = {
+        custom-label-key-1 = "custom-label-value-1"
+        custom-label-key-2 = "custom-label-value-2"
+      }
+
+      custom_taints = [
+        {
+          key = "custom-taint-key-1"
+          value = "custom-taint-value-1"
+        },
+        {
+          key = "custom-taint-key-2"
+          value = "custom-taint-value-2"
+        }
+      ]
+
+      constraints = {
+        fallback_restore_rate_seconds = 1800
+        spot = true
+        use_spot_fallbacks = true
+        min_cpu = 4
+        max_cpu = 100
+        instance_families = {
+          exclude = ["standard_DPLSv5"]
+        }
+        compute_optimized = false
+        storage_optimized = false
+      }
+    }
+  }
+
+  // Configure Autoscaler policies as per API specification https://api.cast.ai/v1/spec/#/PoliciesAPI/PoliciesAPIUpsertClusterPolicies.
+  // Here:
+  //  - unschedulablePods - Unscheduled pods policy
+  //  - nodeDownscaler    - Node deletion policy
+  autoscaler_policies_json   = <<-EOT
+    {
+        "enabled": true,
+        "unschedulablePods": {
+            "enabled": true
+        },
+        "nodeDownscaler": {
+            "enabled": true,
+            "emptyNodes": {
+                "enabled": true
+            },
+            "evictor": {
+                "aggressiveMode": false,
+                "cycleInterval": "5m10s",
+                "dryRun": false,
+                "enabled": true,
+                "nodeGracePeriodMinutes": 10,
+                "scopedMode": false
+            }
+        },
+        "clusterLimits": {
+            "cpu": {
+                "maxCores": 20,
+                "minCores": 1
+            },
+            "enabled": true
+        }
+    }
+  EOT
+
+}
+
+resource "azurerm_resource_group_template_deployment" "castai_onboarding_arm" {
+  name                = var.cluster_name
+  resource_group_name = azurerm_kubernetes_cluster.this.resource_group_name
+  deployment_mode     = "Incremental"
+  template_content       = file("castai_arm_template.json",)
+  parameters_content = jsonencode({
+    "apiKey"                   = {value = var.castai_api_token }
+    "clusterResourceName"      = {value = var.cluster_name}
+    "location"                 = {value = var.cluster_region}
+  })
+}