feat: variable for diagnostic setting metric (#53)

* feat: variable for diagnostic settng metric

* fmt fix

main.tf

@@ -9,6 +9,8 @@ locals {
   # If identity_ids is non-empty, value is "UserAssigned".
   # If system_assigned_identity_enabled is true and identity_ids is non-empty, value is "SystemAssigned, UserAssigned".
   identity_type = join(", ", compact([var.system_assigned_identity_enabled ? "SystemAssigned" : "", length(local.identity_ids) > 0 ? "UserAssigned" : ""]))
+
+  diagnostic_setting_metric_categories = ["AllMetrics"]
 }
 
 resource "azurerm_linux_function_app" "this" {
@@ -162,8 +164,13 @@ resource "azurerm_monitor_diagnostic_setting" "this" {
     }
   }
 
-  metric {
-    category = "AllMetrics"
-    enabled  = true
+  dynamic "metric" {
+    for_each = toset(concat(local.diagnostic_setting_metric_categories, var.diagnostic_setting_enabled_metric_categories))
+
+    content {
+      # Azure expects explicit configuration of both enabled and disabled metric categories.
+      category = metric.value
+      enabled  = contains(var.diagnostic_setting_enabled_metric_categories, metric.value)
+    }
   }
 }

variables.tf

@@ -46,6 +46,12 @@ variable "diagnostic_setting_enabled_log_categories" {
   default     = ["FunctionAppLogs"]
 }
 
+variable "diagnostic_setting_enabled_metric_categories" {
+  description = "A list of metric categories to be enabled for this diagnostic setting."
+  type        = list(string)
+  default     = []
+}
+
 variable "kind" {
   description = "The kind of Function App to create."
   type        = string