The SignUp mechanism enables 3rd party integrations for identity verification and consent management.
If CAPTCHA for Signup flow is enabled. Then this API cannot be called directly as it requires ReCaptchaToken in the payload, which can only be added through UI, when user clicks on "I'm not a robot" checkbox.
Otherwise, If CAPTCHA for Signup flow is disabled, Only user having system administrator or user management permissions will be able to use the API.
This API also has an option to Auto Login the user.