I've added a REST API class (GcpAuthenticationParameters) in an attempt to address #3451 <https://github.com/apache/polaris/issues/3451> - that is, allowing users to create external catalogs that use the GoogleAuthManager in the Iceberg codebase.
I've put together this pull request <https://github.com/apache/polaris/pull/3729> that hopefully implements this. Other than adding an extra enum element to AuthenticationParameters, there are no changes to existing classes. Dmitri Bourlatchkov has told me this necessitates a discussion in the mailing lists and asked me to kick one off. So can I please ask for opinions? Thanks, Phillip
