Provides CSRF protection & validation. This middleware adds a CSRF token to a cookie. The cookie value is compared to token in request data, or the X-CSRF-Token header on each PATCH, POST, PUT, or DELETE request. This is known as "double submit cookie" technique. If the request data is missing or does not match the cookie data, an InvalidCsrfTokenException will be raised. This middleware integrates with the FormHelper automatically and when used together your forms will have CSRF tokens automatically added when `this.Form.create(...)` is used in a view.