server side validation guidance

src/content/docs/turnstile/get-started/server-side-validation.mdx

@@ -269,6 +269,7 @@ It always contains a `success` property, either true or false, indicating whethe
 - `action` is the customer widget identifier passed to the widget on the client side. This is used to differentiate widgets using the same sitekey in analytics. Its integrity is protected by modifications from an attacker. It is recommended to validate that the action matches an expected value.
 - `cdata` is the customer data passed to the widget on the client side. This can be used by the customer to convey state. It is integrity protected by modifications from an attacker.
 - `error-codes` is a list of errors that occurred.
+- `ephemeral_id` returns the [Ephemeral ID](/turnstile/concepts/ephemeral-id/) in siteverify.
 
 In case of a validation failure, the response should be similar to the following: