Fix embedded path ColumnInfo access for composite IDs (GH-2201)

[62hoon99]

Summary

Fix IllegalArgumentException: Cannot obtain ColumnInfo for embedded path when using class-based composite IDs as @Id properties.

Problem

When ResolvingRelationalPropertyValueProvider resolves identifiers for entities with composite IDs, it delegates to DocumentValueProvider.getValue() for embedded paths.
Embedded paths do not have a single ColumnInfo, which results in an IllegalArgumentException.

Solution

Update DocumentValueProvider to properly handle embedded paths:

• getValue(): return null for embedded paths (values are resolved via individual properties)
• hasValue() / hasNonEmptyValue(): recursively evaluate embedded properties

Changes

• Updated MappingRelationalConverter.DocumentValueProvider to handle embedded paths correctly
• Added unit tests for both class-based and record-based composite IDs
• Added integration tests covering ResolvingRelationalPropertyValueProvider behavior

Testing

All tests pass. Both class-based and record-based composite IDs are now handled correctly.

Fixes #2201

Checklist

• I have read the Spring Data contribution guidelines.
• I used the provided code formatters and did not submit formatting-only changes.
• I added unit and/or integration tests that back my changes.
• I added myself as author in the headers of the classes I touched and updated the license headers where required.

[62hoon99]

Recreated this PR from a clean branch to fix history/CI issues.
New PR: #2201
Closing this one to avoid confusion.