[lake/iceberg] thrown Exception when partition columns are of non-String type

[beryllw]

Purpose

Linked issue: close #1821

Brief change log

Partitions in Fluss Tiering split are Strings, but Iceberg partition transforms require data in actual types. For now, we throw an exception and will implement the type conversion later.

Tests

API and Format

Documentation

[Copilot]

Pull Request Overview

This PR adds validation to reject partition keys with non-String types in Iceberg lake tables, as the current implementation only supports String partition types. This is a temporary measure with a TODO to implement proper type conversion in the future.

Key changes:

• Added validation in IcebergLakeCatalog to throw InvalidTableException when partition keys are not of String type
• Added parameterized test to verify the validation works for both primary key and log tables

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
IcebergLakeCatalog.java	Added validation to reject non-String partition key types with appropriate error message
IcebergLakeCatalogTest.java	Added parameterized test case to verify non-String partition keys are properly rejected

Comments suppressed due to low confidence (1)

fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalog.java:1

• Corrected grammar: 'support' should be 'supports' to match singular subject.

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[luoyuxia]

@beryllw Thanks for the pr. Only one comment. PTAL