App Service app has App Service Authentication enabled

# Enable App Service Authentication for an App Service (use azurerm_linux_web_app or azurerm_windows_web_app)
resource "azurerm_linux_web_app" "<example_resource_name>" {
  name                = "<example_resource_name>"
  resource_group_name = "<example_resource_name>"
  location            = "<example_resource_name>"
  service_plan_id     = "<example_resource_id>"

  site_config {}

  auth_settings_v2 {
    auth_enabled = true # CRITICAL: Enables built-in authentication (Easy Auth)
  }
}

// Enable App Service Authentication (Easy Auth) for an existing Web App
resource auth 'Microsoft.Web/sites/config@2022-03-01' = {
  name: '<example_resource_name>/authsettingsV2'
  properties: {
    platformEnabled: true // CRITICAL: Turns on built-in authentication for the app
  }
}