Reset the user's forgotten password.

Entitlements required: resetPassword (Reset password).

Verifies the user's identity by using the last step's method of verification and if successful, changes the user's password.

On Success, an email is sent that the user's password changed.
The email template for branding is at "authentication/login/cloud_directory/password/forgot_password/reset_password_complete.xml".
Pass in the themeId query parameter to brand the email template for notifications.