Recent changes in Iceberg REST deprecated the oauth2 endpoint as part of the REST spec. Instead, the OAuth2 endpoint of the IdP should be used.

Extract from the spec:
The oauth/tokens endpoint is DEPRECATED for REMOVAL. It is not recommended to implement this endpoint, unless you are fully aware of the potential security implications.

All clients are encouraged to explicitly set the configuration property oauth2-server-uri to the correct OAuth endpoint.

It would be great to make the oauth2 server uri configurable by adding a iceberg.rest-catalog.oauth2.server-uri configuration for the Iceberg Rest Catalog.