Consolidate usage of CommitFailedException and CommitConflictException

[dimas-b]

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

See discussions in #1989 for context.

Cf. #1989 (comment)

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

No response

[tmater]

I just want to confirm that I understand the issue correctly.

Currently, in some places, we're using CommitFailedException. While it generally describes the situation and returns the correct 409 response, it's not the best fit since it's an Iceberg-specific exception. In some of these cases, the conflict actually originates from Polaris.

We should review where CommitFailedException is used and consider replacing it with a more appropriate and specific CommitConflictException when the conflict comes from Polaris.

[dimas-b]

Yes, CommitFailedException is currently used by Polaris code to represent eventual 409 errors in the REST API. However, Polaris uses a lot of non-REST Iceberg code and CommitFailedException may potentially occur in other contexts, where it is not clear what the appropriate REST status code should be.

IMHO, it is preferable to use CommitConflictException, which is owned by Polaris and is intended to clearly map to 409 at the REST level.