Single sign-on
One set of credentials logs a user into every application we run for you: the auction website, the native apps, the Manager. A bidder who registered on your website is already known to your app. A staff member does not maintain separate logins for separate tools.
Both audiences, one system
Bidder authentication and staff authentication are usually two different systems bolted together, which is where access problems come from. Here they are one service with different roles, so permissions are decided in one place and audited in one place.
Standards, not invention
The service implements OAuth 2.0. That matters if you intend to connect the platform to your own identity provider or to systems that expect a standard flow — it is the same reason the integration API supports SSO. Two-factor authentication is available on accounts.