terraform resource to enable functionapp and msi to resource group.

functionapp_msi.tf

resource "azurerm_storage_account" "main" {
  name                     = "${var.storage_account_name}"
  location                 = "${var.location}"
  resource_group_name      = "${var.resource_group_name}"
  account_tier             = "Standard"
  account_replication_type = "LRS"
  tags                     = "${var.tags}"
}

resource "azurerm_app_service_plan" "main" {
  name                = "${var.name_prefix}-serviceplan"
  location            = "${var.location}"
  resource_group_name = "${var.resource_group_name}"
  kind                = "FunctionApp"

  sku {
    tier = "Dynamic"
    size = "Y1"
  }

  tags = "${var.tags}"
}

resource "azurerm_function_app" "main" {
  name                      = "${var.name_prefix}-function"
  location                  = "${var.location}"
  resource_group_name       = "${var.resource_group_name}"
  app_service_plan_id       = "${azurerm_app_service_plan.main.id}"
  storage_connection_string = "${azurerm_storage_account.main.primary_connection_string}"
  https_only                = true
  version                   = "${var.function_version}"
  enable_builtin_logging    = "${var.enable_builtin_logging}"

  lifecycle {
    ignore_changes = [
      "app_settings.%",
      "app_settings.MSDEPLOY_RENAME_LOCKED_FILES",
      "app_settings.WEBSITE_RUN_FROM_PACKAGE",
    ]
  }

  identity = {
    type = "SystemAssigned"
  }

  app_settings = "${var.app_settings}"
  tags         = "${var.tags}"
}

resource "azurerm_role_assignment" "main" {
  scope                = "${data.azurerm_resource_group.current.id}"
  role_definition_name = "Contributor"
  principal_id         = "${lookup(azurerm_function_app.main.identity[0], "principal_id")}"
}