Integration of Polaris Catalog with IAM system like KeyCloak

### Is your feature request related to a problem? Please describe.

OAuth2 Authentication and Authorization

### Describe the solution you'd like

From documentation it seems that Polaris catalog also act as OAuth2 server, means OAuth2 based authentication and authorization is builtin the catalog itself. In normal deployment there may be already deployed IAM server. I like to know whether Polaris Catalog provides any integration with external IAM server like keycloak.

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

The issue names OAuth2, Polaris Catalog, and an external IAM server such as Keycloak but provides no files, tests, or entry points. Start by reviewing the catalog's existing authentication and authorization documentation and configuration; done would require a defined external-IAM integration scope and corresponding implementation or documented support.

Written by the indexing model from the issue text.