Unique identifier for the request form to be activated. Must be in base64url-encoded or GUID format (e.g., 'yS86zRG7smz7NVwdUEyJSj'). Obtain this value from form listing endpoints (GET /v2/spaces/{spaceId}/forms) or form creation response. The form must exist in the specified space and be in deactivated state. Activating the form makes it immediately available for users to submit requests.