Implement scanner API for single CRUD transactions

[brfrn169]

Description

This PR adds a scanner API implementation for single CRUD transactions.

Note that we are working on this feature in the add-scanner-api-to-transaction-abstraction feature branch.

Related issues and/or PRs

• Add getScanner() method to transaction interfaces #2698

Changes made

• Added a scanner API implementation for single CRUD transactions

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• I have considered whether similar issues could occur in other products, components, or modules if this PR is for bug fixes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• Tests (unit, integration, etc.) have been added for the changes.
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

N/A

Release notes

N/A

[Copilot]

Pull Request Overview

This PR introduces a full implementation of the getScanner API for single CRUD transactions, augments unit tests to cover its behavior, and removes a placeholder integration test.

• Implement getScanner in SingleCrudOperationTransactionManager with proper exception wrapping.
• Add comprehensive unit tests for one(), all(), iterator(), and error scenarios on the scanner.
• Remove the disabled placeholder integration test without replacing it.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
integration-test/src/main/java/.../SingleCrudOperationTransactionIntegrationTestBase.java	Removed a disabled stub test for getScanner without adding a real one.
core/src/test/java/.../SingleCrudOperationTransactionManagerTest.java	Added unit tests covering scanner methods and error propagation.
core/src/main/java/com/scalar/db/transaction/singlecrudoperation/SingleCrudOperationTransactionManager.java	Implemented getScanner and wrapped storage scanner calls into CrudException.

Comments suppressed due to low confidence (1)

integration-test/src/main/java/com/scalar/db/transaction/singlecrudoperation/SingleCrudOperationTransactionIntegrationTestBase.java:412

• The disabled placeholder test for getScanner was removed without adding an actual integration test to verify scanner behavior against a real storage backend. Consider adding an end-to-end integration test that exercises getScanner on committed records.

@Disabled("Implement later")

[Copilot]

[nitpick] The try–catch logic for wrapping ExecutionException into CrudException is duplicated in one() and all(). Consider extracting a helper method (e.g. wrapCrud(Supplier<T>)) to reduce code duplication and improve readability.

[feeblefakie]

LGTM! Thank you!

[Torch3333]

LGTM, thank you!

[komamitsu]

LGTM! 👍