docs: Add snippet for ReadLockMode configuration at client and transaction

[shobhitsg]

New Sample: Added IsolationLevelAndReadLockModeSample.java to demonstrate Cloud Spanner transaction configurations.

Refactoring: Moved the isolation level example from SpannerSample.java to the new file for better organization.

Dependency Update: Bumped libraries-bom in pom.xml from 26.71.0 to 26.73.0.

[snippet-bot]

Here is the summary of changes.

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• samples/snippets/src/main/java/com/example/spanner/IsolationLevelAndReadLockModeSample.java:32, tag spanner_isolation_level
• samples/snippets/src/main/java/com/example/spanner/IsolationLevelAndReadLockModeSample.java:74, tag spanner_read_lock_mode

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• samples/snippets/src/main/java/com/example/spanner/SpannerSample.java:1558, tag spanner_isolation_level

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[gemini-code-assist]

Summary of Changes

Hello @shobhitsg, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the documentation and examples for Google Cloud Spanner by providing a dedicated sample that illustrates how to configure transaction isolation levels and read lock modes. This change clarifies the application of these settings at both the client and individual transaction levels, emphasizing the precedence of transaction-specific configurations. The refactoring improves the discoverability and clarity of these advanced transaction options within the sample codebase.

Highlights

• New Sample Added: Introduced a new dedicated sample file, IsolationLevelAndReadLockModeSample.java, to demonstrate the configuration of IsolationLevel and ReadLockMode for Google Cloud Spanner transactions.
• Code Refactoring: The isolationLevelSetting example has been moved from the general SpannerSample.java file into the new, more focused sample, improving code organization.
• Dependency Update: Updated the libraries-bom dependency version in pom.xml from 26.71.0 to 26.73.0.

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[gemini-code-assist]

Code Review

This pull request introduces new code snippets to demonstrate the configuration of IsolationLevel and ReadLockMode for Spanner transactions, both at the client and transaction level. The existing isolationLevelSetting snippet has been moved from SpannerSample.java to a new, dedicated file IsolationLevelAndReadLockModeSample.java, which now also includes the new readLockModeSetting snippet.

My review focuses on the new file. I've identified a resource leak where ResultSet is not being closed, and I've provided suggestions to fix this using try-with-resources. I also noted significant code duplication between the two new snippet methods and recommend refactoring to improve maintainability.

[sakthivelmanii]

@shobhitsg You need to write an integration tests for this.