an Identity Management Plugin webhook. When configured, this plugin enables the `AssumeRoleWithCustomToken` STS API extension. A user or application can now present a token to the `AssumeRoleWithCustomToken` API, and MinIO verifies this token by sending it to the Identity Management Plugin webhook. This plugin responds with some information and MinIO is able to generate temporary STS credentials to interact with object storage.

The authentication flow is similar to that of OpenID, however...