Added support for authentication mode for Customers

You can now set the authentication mode for Customers using the Merchant Center. The authentication mode determines whether a Customer is authenticated through a password or an external authentication provider. To view the authentication mode and password of an existing Customer, go to the Security tab of the Customer's details page.

This enhancement makes it easier to create Customers without passwords in the Merchant Center and reduces the need to build custom tooling to manage customers. Previously, you could only set the authentication mode using the Customers API.